Consumer Reports: Overstating gas mileage [EPA figures on gas mileage are off by huge amounts]

wfaa.com ^ | September 20, 2005

[meyer]

Well, FWIW, we drive compacts and the mileage has always been a couple of miles within the advertised. I suspect the problem is mainly with the gas guzzlers, and we wouldn't buy one of those anyway :) In any case, it's still buyer beware, though folks who don't keep their cars well-maintained are shooting themselves in the foot. Can't blame Detroit for that.

Yeah, poor maintenance is a problem. Cars are so reliable today that people never give a tune-up a second thought. They generally don't need it, but things do go wrong from time to time. A bad oxygen sensor or partially clogged converter can have a significant effect on mileage, but until the idiot light goes on, people are oblivious to the situation. Of course, not everybody is like this, but there are plenty of people that won't even get the oil changed every now and then.

I track my mileage with every tankful, since it is a very good indicator of when things are working properly or when something isn't quite right under the hood.

[mewzilla]

I know folks who drive with tires at 10 psi. I know folks who don't bother with an oil change til their engine runs dry. And then they need more than an oil change. Their idea of preventive maintenance is waxing the car. Sigh.

[RightWhale]

a dynamometer. It turns the front wheels

Hmm. Sounds like technology has become so advanced that even Cindy Sheehan can write about it.

[CGTRWK]

The EPA "benchmark" is so far removed from real driving conditions as to be genuinely useless.

There is no air resistance.

The "highway" test is conducted at an average speed of 48mph.

Acceleration is limited to under 3mph per second. Vehicles with cylinder deactivation are tweaked to run the entire test on 4 cylinders.

[meyer]

From the EPA's web site:

"Vehicles are driven over identical driving patterns by professional drivers in controlled laboratory conditions on a dynamometer. Road forces and aerodynamic forces are fully accounted for in the test."

"The city test is approximately 11 miles long and is a stop and go trip with an average speed of about 20 miles per hour (mph). The trip lasts 31 minutes and has 23 stops. About 18 percent of the time is spent idling (as in waiting for traffic lights). A short freeway driving segment is included in the test. The engine is initially started after being parked overnight."

And the highway test: "The highway is a 10 mile trip with an average speed of 48 mph. The vehicle is started "hot" and there is very little idling and no stops."

While the city test doesn't seem too far off of reality, the highway test ought to be done at realistic highway speeds of 65 or 70 mph. Still, my results match up pretty well with what the EPA predicts.

[bill1952]

Being that it is the same for every vehicle, then that is the definition of a benchmark, however removed from reality that you or others perceive it.

That's all it is.

[NCLaw441]

I have the Toyota Prius, since November, and I am averaging overall about 48.5 in real world driving. It isn't as good as advertised, but twice my last car's mpg, and really fun to drive.

[eraser2005]

Late to the party here, but I can tell you I get significantly BETTER mileage than the EPA ratings. I'm supposed to get 19/26 in my Taurus and I get 23/32. Shove that in your pipe and smoke it, CR....

And I know several people who own hybrids, and not a single one of them averages less than 42 mpg (1 civic hybrid and 4 priuses).

Oh, and when CR comes out like they did yesterday and claims that the Mercury Mariner is one of the most reliable SUVs out there, but the Ford Escape and Mazda Tribute are not reliable, I say the standard deviation on their measurements is FAR too great to make any conclusions.

[Wiseghy]

My Civic Hybrid mileage is about 43 mpg, using an automatic in mixed driving.

I can get it up to 48 mpg by concentrating harder on my use of accelerator and lowering my speed. This increased effort on my part generally has no impact whatsoever on my travel time, since traffic delays keep my average speed low anyway.

Since getting a hybrid, I've come to appreciate what TERRIBLE drivers most people are. They tailgate, speed and accelerate way, way too much. This isn't all their fault, since non-hybrids don't generally give folks immediate feedback on how their actions impact mileage.

I'm convinced that a simple feedback meter in any type of car would allow most people to increase their mileage by 10% or more with only a little bit of effort and no increase in travel time.