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From http://cascadiascorecard.typepad.com/bl ... index.html

With gas prices soaring, some people may trade in their gas-guzzlers for more fuel efficient vehicles. But don't trust the EPA ratings. A recent analysis by Consumer Reports shows that 90% of vehicles get worse gas mileage than advertised -- in some cases more than 50% worse for city driving. And nationally, Corporate Average Fuel Economy (CAFE) may be overstated by a whopping 30 percent.

How does this happen? Manufacturers inflate fuel efficiency in several ways. First, they don't test cars the way people actually drive. Vehicles are tested in a laboratory, not on actual roads. And while the EPA assumes that 55% of driving is done in city traffic, which uses more fuel than highway driving, many cars actually spend 62% of time there, according to Consumer Reports. Second, the car they test is not the car you buy. Manufacturers are allowed to use prototypes built especially for the fuel economy test, so they often modify them (within limits) to get the best rating possible.

In 1984 the EPA responded to an outcry by consumers who were angry that they could not get the fuel efficiency advertised. But rather than change the way it tests cars, the EPA just adjusted the test results it reports: 10% lower mpg for city driving, 22% lower for highway. And, as Consumer Reports shows, even these adjusted numbers still aren't accurate, especially in city driving.

And worse, CAFE standards, already low and full of loopholes, are also affected. Automakers successfully lobbied so that only the unadjusted mpg ratings are used when enforcing CAFE standards. While the government estimates that the fleet of 2003-model-year passenger cars that Consumer Reports tested averaged 29.7 mpg, Consumer Reports only got 22.7, well below the current standard of 27.5 mpg. For light truck the difference was 21.4 mpg versus 16, with a standard of 20.7 mpg.

When buying a new car, follow Consumer Reports's advice:

The EPA sticker can help you evaluate relative gas mileage among vehicles, but not absolute mpg.. .. [D]iscount the EPA sticker numbers for city travel as follows: conventional cars and trucks, 30 percent; larger hybrids, 35 percent; diesels, 36 percent; smaller hybrids, 42 percent.
 

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The question remains, how do people drive? If you surveyed this site alone, you can see that MPG due to driving conditions vary from 40MPG to 60MPG. In other words, driving habits vary so much, that it would be impossible to have an 'accurate' EPA MPG.

But I do agree, there should be more fairness such as use of the cabin heating/cooling system (EPA uses none in favorable ambient temps), using production cars, etc. Using dynamos do allow for more precise mesurements which is needed, where on road tests can easily be affected by a gentle wind.
 

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Here is the real lie:

"Manufacturers inflate fuel efficiency in several ways. First, they don't test cars the way people actually drive. "

The manufacturers are required to report the EPA numbers. THe EPA runs the tests. It is against the law to advertise anything but the number sobtained by this federally-mandated test procedure.

Blame the EPA, not the manufacturers. Their hands are tied.
 

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I am continually surprised at people who assume that the EPA mpg figures found on new car stickers are somehow guarenteed performance. The only value I gain from these figures are in making relative comparisons between cars. I asssume that one with a rating of 35 mpg highway might have better real world gas mileage than one with a sticker that says 25 mpg. But, I would expect neither car to give me the advertised mileage.

As to Consumers Reports, I have found thier experience mileage in overall driving (mix of highway and in town driving) to be very conservative for all cars. I have had several new cars over the years and all of them have given me better mileage than CU reports. So, like the EPA figures, I assume that a car they found to give 51 mpg (Insight) would give me better mileage than one that they found to give them 44 mpg (Prius). So, their figures are relative as well.

As to the mpg of the Prius I have, the lifetime mpg (mix of interstate and local) for 8,000 milfes divided by all the fuel I have dumped in it for that 8,000 miles, is approximately 51 mpg or 7 mpg better than CU reported and (surprisingly) less but fairly close to the CU figure. In fact, looking at the mpg for each tank load (not accurate, I know, because of the varience of "full tank" amount and the sensitivity of the variety of pump I have used at many gas stations) has never been worse than 45 mpg and the best was 63 mpg.

Oh yes, my last car was a Ford Explorer and I experience better gas mileage than CU's 16 mpg.

So, take the EPA and CU figures for what they are: relative comparisons between cars, not what you will experience.
 

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DanMan32 said:
The question remains, how do people drive? If you surveyed this site alone, you can see that MPG due to driving conditions vary from 40MPG to 60MPG. In other words, driving habits vary so much, that it would be impossible to have an 'accurate' EPA MPG.
I agree completely. The Prius has taught me how to drive all over again. Now that I've learned to drive for optimal gas economy, I've been hitting the EPA numbers pretty closely. I drive a mix of highway and city (and backroads) and I'm averaging 56.2 MPG over sevaral thousand miles. Incidentally, I've noticed a huge dropoff in gas milage on the highway if I go above 62 MPH. Anyone else notice this? If I go on the highway now, I just set the cruise control to 62 and relax. If feels weird seeing all the cars flying by me in the left lane, but I was surprised that I don't really lose much time getting to work, and I'm a lot more relaxed when I do arrive. :)
 

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I've taken two long trips in Phoebe - mostly expressway driving and I've driven the speed limit all the way. Tennessee's speed limit is 70 and other states mostly 65. I can't say I've noticed a significant difference when I set the cruise control at 70 as opposed to 65. As long as I use the cruise control I pretty consistently get 56 - 58 mpg on x-ways. Of course, that figure also includes a small amount of off x-way driving, too.
 

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I just drove to VA from FLA, with the AUTO TRAIN doing most of the work. But, what I did drive for the whole trip, was about 1000 miles. And the car was loaded, plus used the A/C the whole time. I used the cruise almost all the time as well.

And I got, on average, 52 MPG on the Highway.

Speed limits were between 55 and 70 on the highways. So, I am happy with that.

And my Prius now has just under 2000 miles total on the car.
 

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Uhhhh, you folks who say you're getting the same mileage at different freeway speeds? You may want to recalculate.

I get hugely different numbers even at five MPH stages. I can't imagine that ANYBODY is getting the same mileage at 70 as they do at 65 or 60. No way. If you are, then all other things are not equal. You're driving with a tailwind. Or you're going downhill. Or making one trip with a lighter load.

My point is SOMETHING is different.

I'm getting nearly a 10-MPG improvement when I drive 55, as opposed to 65.

It's all about wind resistance. Unless something else has changed, that is.
 

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BIF said:
Uhhhh, you folks who say you're getting the same mileage at different freeway speeds? You may want to recalculate.

I get hugely different numbers even at five MPH stages. I can't imagine that ANYBODY is getting the same mileage at 70 as they do at 65 or 60. No way. If you are, then all other things are not equal. You're driving with a tailwind. Or you're going downhill. Or making one trip with a lighter load.

My point is SOMETHING is different.

I'm getting nearly a 10-MPG improvement when I drive 55, as opposed to 65.

It's all about wind resistance. Unless something else has changed, that is.
I said, 'average'.

As in, well, average. Not the same each time.
 

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On a (reasonably) flat road I can average 50MPG at 70MPH. I've done it on I-95 in Georgia/Florida.

I don't think the risks of going slower than traffic is worth the gas savings. Semis love tailgating, to make a "go faster" point or something.

October means another trip to Florida for lottery tickets, and I'm hoping to come close to last October's 54MPG round-trip results. It's going to be nearly $30 instead of less than $20 for the required tankfull, and I've only won $5 so far...
 

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DanMan said:
I think Bif was focusing on janets98's post. 58MPG doing 70 is not plausable to me.
Perhaps, if she began her trip in the mountains of Tennessee and ended it at the beach in North Carolina, she would see 58 MPG. Lot of coasting there…
:D
 

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nh_jim said:
If I go on the highway now, I just set the cruise control to 62 and relax. If feels weird seeing all the cars flying by me in the left lane, but I was surprised that I don't really lose much time getting to work, and I'm a lot more relaxed when I do arrive. :)
My wife calls this "the expanding universe." With our old Dodge Colt - nicknamed the nag, since it was far too old to be a Colt - the expanding universe was mandatory, because the only way to get that car to 75 mph was to drive it off a cliff. With the Prius, we CHOOSE to inhabit the expanding universe.
 

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Well, I could swear that's what the screen says I averaged. But now you've got me wondering if I was delusional.
Next time Phoebe and I go for a lengthy trip I'm taking the digicam to document what I get.
Then we'll know for sure.
 

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KTPhil said:
The manufacturers are required to report the EPA numbers. THe EPA runs the tests.
Actually, I was surprised to recently read (I think it was in the newest Consumer Reports) that the manufacturers run the tests, in accordance with the EPA regs.

rpm
 

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I just filled up and with a total of 4676 miles on the odo, I got my first 64MPG tank! In fact, that is now an average of 54MPG over the past 491 miles!

6 tanks ago, I had to fill twice with 89 octane and that apparently killed my building MPG numbers (nothing else had changed). 4 tanks ago, I was able to fill both times with 'pure' 87 octane, and the numbers returned to the normal (for me) 48-50mpg average. 2 tanks ago I bumped pressure from 38front/36rear to 42front/40rear and am now scoring the 54 average with the high of 64! (I had originally intended to go 42/40 but my home compressor is weak and apparently I only got 38/36...oh well.)

Now, to be honest, the temperatures around here have fallen about 10 degrees F; not enough for me to turn off the AC though :)
 
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