EPA Fuel Economy Myth: Too High, Too Low? 1378
ThosLives asks: "I have seen here on Slashdot , and just about every other publication, numerous articles about fuel cells, hybrid vehicles, and the inaccuracies of EPA fuel economy stickers. For instance, today there is a review of the Toyota Prius that had the famous line 'Since no car really achieves the EPA estimated mileage...' I happen to drive a car with an EPA sticker of 21 city 25 highway (all figures in miles per gallon). I've driven the car for 47000 miles and the lowest I've ever seen is 23 and some change; the highest, 36.3 (I'm probably about 60% highway 40% stop-and-go and yes, the high was on a long highway trip). My all-time average is about 28.5. As most people get less than the EPA mileage, how does the Slashdot readership fare when it comes to EPA sticker vs actual experience, and on what type of vehicle?"
"Am I a rare breed that can drive my car (2.0L I4, 170 HP, 6-speed manual) aggressively (I've had coworkers and friends say 'woah!' more than I'd like to admit *grin*) and still stomp the EPA sticker? Did I get lucky with a phenomenal car? Am I enough of a counter-example to thwart the belief that the EPA figures are 'too liberal'? Are fuel economy issues just FUD from [insert lobby group of choice]? Or is the answer simply 'it depends on how you drive, what you had for breakfast, and the color of your neighbors' cat?'"
about right (Score:3, Informative)
city gets lower than the 22 rating, around 18.
Ford Escord and Mini Cooper S (Score:4, Informative)
I used to have a standard 96 Ford Escort (no AC) that regularly got around 30-35 MPG in about a 60/40 Highway to "City" split. I can't remember what the EPA numbers were for that model, but I remember that I was around or slightly above them.
I now have a MINI Cooper S (fun f**king car). Under the same driving conditions I was getting about 23-24 MPG, which was lower than EPA. I have since moved and the drive is now 30/70 HW vs City and it has dropped to the 21-22 MPG range.
About what I'd expect... (Score:4, Informative)
Look it up here (Score:5, Informative)
70 MPG in the Insight, depending on weather! (Score:5, Informative)
Driving at moderate speeds is also a big factor.
same story here (Score:3, Informative)
I've heard it said that a typical vehicle gets the best mileage at 55 mph, and that for every 5 mph above or below that, subtract 1 mpg. I'm an aggressive accelerator, but I rarely go much over the speed limit any more, so this might be where some of my luck comes from. In fact, the best mileage I've ever gotten was when following my father-in-law when he was driving a moving truck at about 55-60mph the entire stretch from Chicago to Kansas City.
depends on everything (Score:2, Informative)
Now what is interesting, but not really surprising, is I get the best gas mileage from my V8s. They work a lot less than the 6s and 4s I've had when you get on the highway [car body design is a great factory in this, obviously
Prius -- Real Numbers (Score:2, Informative)
Driving habbits matter. My wife (lead foot, middle name of "Never Say Brake") gets a good 10 points worse than I. Short hops in city/suburb traffic will lower the gas mileage down to the low 40's. Careful use with highway/rush hour traffic will push it toward 60.
It is like anything else. Your mileage may vary, but for me, the government underestimated the mileage.
Re:Ford Escord and Mini Cooper S (Score:5, Informative)
It's really a quick and a smart thing to do and I encourage everybody to do it. Your fuel economy will be one of the first warning signs that your car is developing a problem. If that drops it's time to take the car to get looked at. Just a little time to save major money on repairs later. And if you go to sell your car you have a record of its health.
Re:what's an EPA sticker (Score:3, Informative)
Hi Timmy! (Score:3, Informative)
The slashdot readership has probably faired the same since this story originally ran [slashdot.org]. Oh, wait.
Motorcycle! (Score:2, Informative)
Many, many factors to consider... (Score:1, Informative)
2) Condition of individual vehicle and quality of maintenance
3) Location and altitude
4) Type and quality of gasoline used
The list goes on... all of these factors are beyond the control of the EPA and will affect your mileage. There are also build tolerances involved... no two cars will produce exactly the same amount of power, nor the same mileage.
Wanna improve your mileage?
1) Change the oil regularly (also #1 way to help your engine live a long time - try synthetic if you can afford it)
2) Inflate the tires properly
3) Make sure the exhaust is clear and catalytic converter isn't plugged (exhaust shop can check this if you're getting poor mileage)
4) Change the oxygen sensor(s) at their service limit
5) Change the air filter regularly
6) Don't carry extraneous junk in the car/truck (reduce the weight)
7) Use a good quality gas of the octane level required by the vehicle
8) Get regular tune-ups
9) Accelerate evenly... stabbing the gas pedal hard forces the ECM to enrich fuel to produce maximum power - but poor economy results
There are many, many other things you can do, but not too many readers are going to want to clean and repack their wheel bearings (where applicable) every so many years...
Ford Focus SVT (Score:2, Informative)
Re:what's an EPA sticker (Score:2, Informative)
The test is completely artificial, being run on a dynomometer (no hills, wind, weight in the trunk, etc.) but has the considerable advantage of no being subject to these same variables when the test is run.
EPA established this test for emissions testing, but the government has made the results of this artificial test both required and the only allowed gas mileage estimate car manufacturers are allowed to post on the new cars.
Good -- consistent, easily compared, verifiable
Bad -- not representative of actual usage. Misunderstood by many consumers.
Re:Thus the phrase... (Score:5, Informative)
I own a 2004 Prius, and I must say that I DON'T get the mileage advertised, although I have seen per-trip variations outside what I so-far consider my normal range. My own figures are closer to 47MPG (combined) for the life of the car, now at 4000 miles. However, my style of driving tends to be shorter trips taken in a hilly locale--both of which negatively influence mileage. Slightly longer trips (a daily commute of 60+ miles) and flatter terrain (coming north to town on the coastal plain) allows a friend here (also with an '04 Prius) to average 53 or so. All other factors seem similar--we have similar driving styles, same tires at same pressure, etc.--but there's a big difference in the mileage figures for the same car. I don't think the EPA takes this into account; they're looking at a bad extrapolation of data based on emissions and a short test--almost a perfect, no-wind, flat-land drive.
I believe the Prius is a good, capable machine. I can see how, in the right circumstances, the car would do as well as, or better than, the EPA figures. Lots of folks do it.
Check out Greenhybrid.com [greenhybrid.com] and Prius Chat [priuschat.com] and see what others have to say.
My Hybrid Civic (Score:5, Informative)
Re:I drive a 2000 Chevy Lumina. (Score:2, Informative)
That's my experience anyway.
02 Prius (Score:5, Informative)
They changed the cars (Score:3, Informative)
Call it optimizing for the benchmark.
Re:Mine is about what is expected (Score:3, Informative)
This frustrated the hell out of me for a really long time. Then I inflated the tires all the way to near their "max pressure" rating and suddenly my milage is way better than before.
So yeah, I'm a moron for not checking this sooner, but JFC, you'd expect them to properly inflate the tires when they install them!
This does bring up a question though: should tires be inflated to their stated maximum, or below that? If so, how far?
(this assumes cold tires)
Re:Everyone seems to know their rating (Score:3, Informative)
Fallout from the gas crisis of the 70s - our government has mandated that cars produce certain mpg or they get hit with a "gas guzzler" tax, which tops out around $4000 for the biggest drinkers - Vipers, Lamborghinis, etc.
Also the mpg is on the sticker as a shopping guide for comparison purposes for those who care about such things. Exempt from this are large trucks/suvs, which of course get the worst milage and don't pay a gas guzzler tax.
Corvettes (Score:5, Informative)
Its replacement, a 2004 Z06, is stickered at 19/28 and I'm seeing 18.5/33-35 quite respectable and 405 hp to boot.
I love it when some econo-box criticizes my sports car as a gas guzzler and finds out I get better milage than they are
Re:Thus the phrase... (Score:5, Informative)
Re:I drive a 2000 Chevy Lumina. (Score:3, Informative)
Actually, that 305 can take virtually any intake from a smallblock chevy. You can get them at junk yards, but I'd recommend a nice aluminum one. Summit has the Edelbrock Performer intake for $114. I liked the Edelbrock carbs too, but lots of people like Holley's. You could always get a Quadrajet and a cast iron manifold for cheap from the junk yard. Generally smallblock parts fit all smallblocks. There was a change in the bolt pattern in '87 I believe, but if you get parts for the same year engine, you won't have a problem. (unless it's a smallblock 400, but that has it's own issues).
With a 4bbl, as long as the secondaries are closed (you'll hear it when they open, don't worry), it's effectively a 2bbl carb. When the secondaries open, you have more power.
I found that having a 4bbl, it can save gas, if you still drive gentle. The 4bbl gives you the power to move. With a 2bbl, you stand on the gas, begging for it to move, and it takes a lot longer to perform the same manuver (like passing, or accelerating from a stop). If you get greedy with the power (like most of us), of course you'll use more gas.
Back in the day when I was learning to work on cars, I firmly believed using carburators. But fuel injection does give much better fuel efficiency, and better power in stock configurations. Plenty of guys will say that they can make more power with a carburated car, but hey, if you're upgrading, you can upgrade fuel injection too. It just costs more.
Re:Author fails to realize one thing.. (Score:5, Informative)
That's not exactly true. [usatoday.com]
Re:70 MPG in the Insight, depending on weather! (Score:2, Informative)
Batteries are sensitive to temperature. I guess this has to do with them delivering energy via a chemical reaction.
Re:Gas (Score:5, Informative)
Higher compression engines, or more highly-tuned engines, need higher octane gas. Mostly, it's to prevent knocking (early detonation caused by compression rather than spark). Any good car of relatively recent make (at least the past 10 years, if not older) will have a knock sensor to adjust for lower-octane gas, at the expense of fuel usage. However, if your car is designed to run on 87 octane, higher test gas shouldn't make much of a difference.
Actually, there is less energy potential per gallon in higher octane gas than lower. That's not really an issue, though. What most likely happened was that previously you were not using the proper octane-level gas for your engine's compression and the ECM was adjusting to a less optimal program to compensate. As a side note, race gas and airplane gas have much higher octane ratings due to the use of lead additives. Don't try this in your car. Lead will kill your cats in a matter of minutes, not days or months. Race cars and airplanes don't have catalytic converters.
First off, most additives are snake oil. Pretty much the only thing that works is Techron (and knock-off brands using a similar formulation). If you fill your car at a station with Techron or a similar cleaning additive, there's no reason why you should have to add injector cleaner on your own. If you must, an application once or twice a year is sufficient. Any more often and you're just throwing money away. As for better gas giving you better mileage, that's true up to a point. As I mentioned already, higher compression engines require higher octane fuels. If you're not using the right fuel, your engine will operate inefficiently. Using a higher octane gas than is required is useless if your car can't adjust its compression ratios to make use of it (ie, putting 92 octane gas in a low compression engine like many American-made engines isn't going to help anything, while putting 87 octane in a high compression Porsche engine is going to give you poor performance and mileage). If it's bad gas you're worried about, the most common problem is too much water in the gasoline. You can solve this problem with an alcohol additive to "dry" the gas. Other problems like too much sulfur (I believe that was the problem recently with some gas down in Florida, among other places) don't have an easy remedy, and all you can do is stop driving, have the car towed, and empty the tank. Run a few tanks of good gas through the engine and it'll be fine.
As others have already stated in this article, there are many other factors to consider. Low tire pressure, dirty air filter, oil, oil filter, bad alignment, too much weight (of the driver, passengers, and any cargo), etc will all have an effect on your mileage. Also, most cars will get their best mileage at low RPMs. If you can cruise at 2000RPM, you're going to get much better mileage than cruising at 5000RPM (just be careful -- you're going to be in a high gear to cruise at such a low RPM, and trying to accelerate in that gear could cause you to lug your engine. This is more important in high-revving, low-torque engines than it is in low-revving, high-torque engines).
Links:
Re:Gas (Score:2, Informative)
There are so many many variations possible when driving, that 2 trips hardly counts as a test case. A/C, out door temperature, speed limit, construction delays, stops, traffic, change in air pressure, passengers, tire air pressure, temperature of fuel, humidity, rain on the road, wind speed and direction. And yes these will all give variations - some more then others of course.
In fact just filling up the tank can give you variations - how do you know how accurate your gauge is? I can overfill my tank by 5 gallons, it won't register on the needle (still just F), but the fuel is there. The temperature of the gas can change how much volume equal amounts (mass) of fuel will take. Colder temperature you'll get more gas in the tank.
But octane will not make the slightest difference in milage for a vehicle that is designed for 87. If your vehicle is designed for 92 or can advance the timing then maybe - but then you are not supposed to use 87, so again not a comparision.
Howstuffworks "What does octane mean?" [howstuffworks.com]
Federal Trade Commission: Are you tempted to buy a high octane gasoline for your car because you want to improve its performance? [ftc.gov]
You can find more links on your own.
Different States, different Gas (Score:2, Informative)
I Love My Bike. (Score:5, Informative)
I'm riding a Honda Rebel around town now. The car I replaced with the bike was a 1992 Toyota Corolla that pegged in at about 30 MPG on the highway and 21 on the city streets. Since most of my driving was city streets, I'd have to fill up every week or less, depending on the travel schedule. The cost of gasoline now would make my average trip to the station about cost between $25 and $50 per week, again depending on how many times I needed more gas.
I've had the bike for about 2 months now, and I think I reached $50 total in gas this weekend. I haven't figured out the total mileage yet; when the tripmeter reaches 150 miles, I get paranoid that I'll have to cut in the reserve (2.1 gallons in the primary, .6 in the reserve) so I fill up. I always go in and put $5 on the counter, fill up the bike, and go back and get my change. I'm guessing that I'm hovering around 80 MPG.
And I'm getting a tan while I run errands.
Re:Gas (Score:5, Informative)
"Supreme", "92 octane", "premium", whatever you call it- is not *better*. It has a higher octane rating. Oddly, that just means that it's more difficult to ignite it.
If you're getting better gas mileage with it, that means your engine is probably suffering from pre-ignition, aka "pinging", without it. It doesn't mean the higher octane gas has more energy, just that you don't have a cylinder or two working against the rest of the engine. I used to have a jeep that was terrible with pinging unless I used 92 octane, so I am familiar with the situation.
But for most cars, the 87 is just fine. Note that the 92 doesn't have more cleaners or anything else in it. For the vast majority of cars, 87 works fine and there is no reason to get ass-raped by the filling station for 92 octane. It's like shoe size: a size 13 shoe isn't "better" than a size 8, unless your feet are size 13. If your feet are size 8, however, the size 13 doesn't offer you anything more.
The FTC has considered regulating the oil industry by disallowing any terminology suggesting that higher octane is better.
The Low-Down on High Octane Gasoline [ftc.gov]
Re:Mine is about what is expected (Score:3, Informative)
Look in the door jam, glove box or on the back of one of the sun visors for the manufacturers' recommended tire pressure. Usually around 30-34 psi. Don't go by "max pressure" on the sidewall of the tire.
Nope. Use the max pressure on the sidewall of the tire. The places you've suggested will speak *only* of the tires that were installed on the car by the manufacturer. Worse yet, some cars will put low numbers like 22psi or less, to give you a smoother ride, and eat up your gas mileage like there's no tomorrow.
Using the number on the sidewall of the tire you're guaranteed to always have less than the maximum pressure the tire is rated for. Why? You may ask.
I will tell. ;) The max pressure rating is for cold tires with cold air. Unless you're like me and you happen to have an air compressor in your driveway, you'll have to drive to a place to get your tires checked, and they'll be hot (or at least hotter than cold).
The only catch is, if you live in a place that actually has seasons (so, nowhere in the southwest or the south) then you'll need to check your tires at least once a week starting in the springtime and heading into early summer. Then you can drop back to once a month again. The higher summer temperatures could cause any extra air you have from adding air in the wintertime to expand enough to push your tires beyond the max rating, although it's unlikely to pop them.
Most tires will still go another 14-18psi over the max rating with no trouble, albeit with a noticeable loss of traction. Whenever I take a trip I usually throw 5 more pounds in my tires to get better mileage on the highway (the longer the trip the more I worry about it, that stuff will add up over the length of the trip, and if I can have another $20 at the end of the trip not spent on gas that means I can buy more soda for the ride back ;) )
But when it comes right down to it, the only reliable spec you have for the tire you're filling is the spec moulded into the tire. All other specs are unreliable because there's no way to verify that they refer to exactly your tire.
Re:Mine is about what is expected (Score:3, Informative)
One says: Use the number on your doorjamb or glovebox, the other says to use the maximum on the sidewall.
I say: Something in between!
For example with my WRX, the max on the sidewall of the RE-92s is 44psi. The recommended pressure from Subaru is 32psi.
It is a well known that running at the manufacturer's recommended pressure is designed to give a nice smooth ride and still be high enough to lose a bit of pressure and not have to worry about overheating the tire on the freeway.
Similarly, the tire manufacturer is going to design some amount of error into the maximum pressure that the tire can hold to account for in-accurate gauges and temperature changes. I have heard that the tires can hold over 90psi without blowing up, so you should have plenty of headroom.
However, what does happen at higher PSI ranges is that the tire will start to balloon, and you will find that the center of the tire will wear faster than the edges. At this point you will also start to lose traction. You will get better gas mileage, though!
I have found that in general running somewhere around 2/3's of the way between the car manufacturers recommended pressure and the tire manufacturers maximum pressure seems to be a good compromise between comfort, even tire wear and gas mileage. You should also experience an increase in overall traction and more even tire wear if you corner agressively as the lower pressure settings allow for excess flex in the sidewall loading up the outside edge of the tire. For me this means running about 40psi. I also like to run 1-2 psi lower in the rear, to account for the fact that in general there is less weight being carries by the rear tires, so this gets you a more consistent contact patch from front to rear of the car.
Of course, YMMV, and you may want to adjust your tire pressures to your vehicle, tires, driving style and road conditions.
Turbochargers and you (Score:3, Informative)
Of course, at low rpms the effect isn't very noticible because you'll still be generating an intake vacuum - only it'll be slightly less than a naturally aspirated car. Now it depends on the turbo and what its compressor map [google.ca] looks like, but even a little gas (like when cruising) will spin the turbo fast enough to significantly cut down on intake vacuum. Get on the gas a little though, and you should see the vacuum decrease to the point of equilibrium, where the turbocharger is compressing air approximately as fast as the engine could suck it in by itself. Up to and including that point, its relatively easy for a turbo to move air because theres very little resistance. Above and beyond that though, you start generating positive pressure (boost), which is where the real work begins, drivers start having fun, and the fuel economy goes to shit. But nomatter what the engine is doing, the turbocharger is always doing its job, or at least trying to. Even at very low engine RPMs, your turbo can still be spinning at 10,000+ rpm, which is gonna move a little air no matter how you slice it.
So yes, parent is right. Turbocharged cars are always turbocharged. Its a common mistake to assume that your turbo isn't doing any work until it starts to generate positive pressure (boost).
Now get out there and enjoy the power-snails people!
Re:50 MPG Jetta TDI (Score:2, Informative)
Timing Belt kit from Dieselgeek $175
Special tools (also DG) $229
VAG-COM software and cable $249
Grand total $ 653 + S&H + some random other tool purchases. Add in the short shifter and a few other things I did, and I'm in it for about a grand + 8 hrs of my time doing the change. Next time will be quicker (half maybe?), since I went slow following the excellent guide from Fred's TDi Club (tdiclub.com).
Average price I read online for this service was about $650. It ranged from $600-1000. I like working on my own vehicles, so went for the DIY option. Fortunately VW has a new timing belt that goes for 80K miles instead of the standard 60K (40K for automatics!)mile belt that came on all TDi's through 2002. Supposedly VW opted for the belt for noise reasons. Personally, I could care less, a chain isn't going to add that much noise. If properly covered, should be negligible difference over the sound of the diesel anyway and be good for 200K+ miles.
I have some tire/alignment problems right now, and am only getting 42-44 mpg. Prior to those problems, I was getting 48.
I'm only running dino diesel right now, but am considering blending with biodiesel. That's the nice thing about diesels that most of the hybrids can't claim, you can use a renewable energy resource. No net carbon added to the atmosphere (running B100).
Re:Your Prius - your neighbor's Land Cruiser (Score:3, Informative)
Re:50 MPG Jetta TDI (Score:3, Informative)
A significant reason diesel engines are more efficient is because their compression ratios are in the range of 12-24 typically, whereas gasoline engines are much lower. Since only air is present in the cylinder during a diesel engine compression stroke autoignition cannot occur, whereas a fuel-air mixture is present in the compression stroke of a gasoline engine, and autoignition can occur more easily, limiting the maximum compression ratio.
Efficiency of an ideal Otto cycle (which is the cycle used to model both gasoline and diesel engines, assuming Rc for the diesel cycle is equal to 1 for approximations) equals 1-1/((compression ratio)^(k-1)) where k = 1.4 for air, approximately. For a typical gasoline compression ratio of 8 we get an maximum possible efficiency of 56.5%, whereas for a diesel engine of a compression ration 18 we get a maximum theoretical efficiency of 68.5%, approximately. Bear in mind that these are the theoretical limiting cases, friction and other energy losses lower the practical efficiencies; however these losses are present in both gasoline and diesel engines. And for nitpickers, yes, there are a lot of assumptions being made here, &c. &c. &c.
Re:Driving Habbits (Score:3, Informative)
The catch is, there is only a benefit if you accelerate no more than necessary. Thus accelerating quickly on a highway on-ramp yields a gain if you stop at the same cruising speed. If you streak from stoplight to stoplight, you only waste fuel reaching an unnecessarily high peak speed only to dissipate that energy when you apply the brakes.
Re:Economical? (Score:5, Informative)
Note that US gallons (3.6l) are different from imeperial gallons (4.5l), so that can lead to some confusion between UK and US posters!
MW
Driver & More makes a difference (Score:2, Informative)
I've always tracked my mileage by going from full tank to full tank, but lately I found a palm app called "Fuel Log" (Open Source Free SW = cool) and have been using this for the last several months to track our milage.
This is where things get odd... The sienna over the same city/suburban driving routes with the same driver consistently gets better gas milage than the camry, like 21 vs 19. But on the highway, the camry does better, usually around 27, vs 24-26 for the sienna. When I drive a specific car it always gets better gas milage than when my wife drives it. I tend to drive harder than my wife does... go figure
Our previous vehicles usually did much better than EPA ratings. My old Escort GT was rated 25/30 I believe, and I never once got below 30, usually averaged around 32, and got as high as 35 on a couple of long hwy trips. My wife's old Mercury Tracer would consistently beat it's 29/35 EPA rating, and on a couple of long trips even topped 40mpg... Our even more previous car (94 honda accord) was much the same way.
Leads me to wonder if Toyotas simply don't match well to the EPA test. Who does these tests anyway? The manufacturer or the EPA or some 3rd party? Anybody Know???
Keep in mind that EPA cycles probably make the assumption that you stick to the speed limits
Re:Possibly the best post on /. (Score:5, Informative)
However, heavy lobbying (GM, C and Ford) managed to get defense contractors and other contractors, landscapers included in the scheme.
In the late eighties creative accountants started to include ordinary companies like small entrepenurs and got IRS approval for this. When the SUV market exploded in the nineties it became common for everyone with a small company (dentists, doctors etc) to get the tax break.
It's allways possibly to debate what came first; the tax break or the SUV (as an evolution from the truck and the station wagon)?
I think the SUV would have appeared sooner or later as an evoutionary thing within car industry but it would never had gotten so widespread without the tax break. And the truck segment would have been far far smaller than today.
The tax break is a protectionistic piece of shit mutated far from the original concept without any thought of the consequences, be it environmental, energy policy or foreign policy. If someone where to write a book on how special interest is allowed to corrupt US policy on several areas the SUV tax break case is a perfect example.
And BTW to the root poster that brought up this topic: The tax break is far greater than $4000. According to Taxpayers for common sence it's possible get tax break around $100000. They site an example [taxpayer.net] where a business owner can buy a $110000 Hummer and deduct $106000.
+80 miles per gallon (Score:1, Informative)
Sure, you only get horsepower of 34, but still. The car is ultra-cheap. 7500 EURO.
Someone to beat this.
Re:My 1971 chevy Nova got.... (Score:2, Informative)
I've got a VW Jetta TDI and I consistantly get > 50 MPG (average about 52 MPG) in mostly highway driving. Also, around here diesel is 20 cents cheaper than regular.
Re:Thus the phrase... (Score:2, Informative)
The Hummer H2 is built on a Chevrolet Suburban chassis.
As far as power, it is underpowered if it only has 350 HP. Compare that to a V6 Accord which has 240 HP engine to move a ~3500lb car. Fuel consumption will be higher because the driver will tend to run the engine at higher RPMs to extract more power.
As far as automatic transmissions, the reason they generally have slightly lower gas mileage is due to the torque converter, which is a fluid coupling. Energy is lost trying to overcome the viscosity of the oil in the converter. Of course, many modern auto transmissions use lockup torque converters to overcome this drawback.
They are Low... (Score:2, Informative)
We had a locally built rig to use to check the mileage. It was a 1 gallon container, an electric fuel pump, a pressure line and a return line. We would connect it up to the vehicle, start it, and run it out of fuel to start the fuel system completely empty. Then we would put exactly 1 gallon of gas in the container, record the mileage on the vehicle,as well as the mileage on the chase car (to verify the odometer was correct) and both cars would take off. We made sure to drive the car easy without being a grandma driver, no hotrodding or heavy acceleration. Simply going with the slower flow and keeping within the speed limits. We would drive until the car drained the gallon container. Then we pulled onto the shoulder and compared miles traveled.
The route was planned to include a mix of city and highway driving in hopes we would end up with miles traveled in between the 2 advertised numbers. The route included about 6 miles of in town traffic, with at least 3-10 stops, depending on the lights and traffic, and 5-20 mile stretches of open highway in between.
We performed this task no less than 10 times during my 7 year stint at the dealership and the results were fairly conclusive. It beat the advertised highway mileage *every single time*.
Re:Thus the phrase... (Score:3, Informative)
To be more on-topic: The EPA Estimates (there's a keyword for ya! It sounds much more marketable than "wild-ass guess") really only serve to try to compare one car against another, thinking only in terms of gas miliage. My daily beater was rated at 27/37 when it rolled out of the showroom in 1997. I've gotten it as high as 43 (78 mph avg. speed, novemeber, from somewhere in Indiana to somewhere just south of Milwaukee, late at night. Doesn't make sense to me, either, but I did the math four times, just to be sure), as low as 18 (probably burning an eighth of an inch off the clutch and a quarter off the tires in the process), and I usually see about 30-40 for my daily commute (35 miles each way, half the time in heavy traffic, almost all the time on city highways). I religiously check my gas miliage (it's a great early warning indicator!), and I've played with some different variables in the car's 270k miles.
I've found that tire pressure really does take away a couple mpg, after slightly deflating a set of tires I was getting ready to replace. I measure no difference in miliage among dino oil, syn-blend, or synthetic. A nasty air filter will cut an mpg or so off. Winter is always worse than summer, all else being equal.
The biggest gain, however -- the one that got me to 40mpg on my commute -- is shifting behavior. No shock, really, but I didn't expect the gain that I was able to acheive. If I let the engine rev, it's a lot more fun, but I'll pull low-to-mid 30s. If, however, I wait until the RPMs in my current gear are just about 100 over the "lugging point" in the next higher gear, and shift at that moment, I get into fifth really fast, I don't lug the engine (that's really bad. don't do that. you might save some gas, and some effort, but pulling motors out -- especially tranvsere ones -- is a real PITA that you just don't want to do), and I push my miliage to around 40. It seems like I get just a couple more miles out of a fillup if I rev-match instead of using the clutch. Double-clutching drops about 25-50 miles off my fillup total...
If that's too much work for you, buy a bike. Mine gets between 60 and 70 mpg, riding solo, and being extremely heavy on the throttle. I can't bring myself to old-lady the poor thing, so I'm not sure what I could get it up to...
True fuel efficiency means... (Score:3, Informative)
BAD MPG is from 70's soviet union made vehicles which is about 30 MPG and modern cars get around 60-70MPG. We pay 1.2 Eur/litre =~ 5.67$
If US would get anyway near similar TAX on gasoline [Passed with reduction of other taxes] Your thinkin 30MPG is good fuel economy would change. Also that would bring small shops closer to places where people live in order to reduce driving.
Re:Thus the phrase... (Score:5, Informative)
Re:So what's the secret? (Score:2, Informative)
Re:Thus the phrase... (Score:3, Informative)
Because people think of diesels as slow, noisy, smelly, with a fuel that isn't at every gas station. And often, you have to pay extra for all those features.
Of course, the government is looking at ways to fix this. About 20 years since it was pointed out to them, they are finally about to change the requirements on diesel fuel such that the quieter, faster, less smelly, and cheaper diesels sold elsewhere can be sold in the US. (check on the sulfur content of diesel for more information)
Re:Thus the phrase... (Score:3, Informative)
I wouldn't swear you are mistaken, but there is a non-hybrid Lupo [volkswagen.co.uk] that gets that.
Diesel? Depends on your goals. (Score:4, Informative)
Yes, turbo diesel cars get incredible mileage, but the particulate emissions -- despite dramatic improvements over the past decade -- still fall near the bottom of the heap.
So, if you want to improve your mileage to save a couple of hundred dollars a year and/or to reduce dependance on foreign oil, a diesel is definitely the car for you.
On the other hand, if you're concerned about that grey haze hanging low in the sky that you notice every morning driving to work and wonder about what [commondreams.org] it's [californialung.org] doing [airinfonow.org] to [healthandenergy.com] your [ec.gc.ca] lungs [bbc.co.uk], you might want to consider other technologies.
Re:Thus the phrase... (Score:2, Informative)