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Re: EPA Mileage "estimates"

Panjandrum said:
I don't know how they come up with these things, but nobody ever seems to get anywhere close to the mileage estimates in any vehicle.
I've beaten the EPA highway number in three different cars, in driving that is about 70% highway. However, all three have (had) manual transmissions and were not hybrids.

Two hypotheses:

1. Manufacturers can tune cars with automatic transmissions to optimize shifting for the EPA test. Considering that the test cycle is well known (to manufacturers) and many of them will do almost anything to get an extra mpg out of the EPA test (low rolling resistance tires, 5W-20 oil, etc. -- even on non-hybrids), it wouldn't be hard to believe that cars with automatic transmissions have shifting points tuned for the EPA test. Manual transmission cars are not so tunable, since the EPA test driver is supposed to shift at specific speeds -- setting the gear ratios for a manual transmission for the EPA test may result in a car annoying to drive. So it is possible that the EPA test overestimates automatic transmission cars but underestimates manual transmission cars.

2. A hybrid starting the EPA test with a full battery may end the test with a partially discharged battery. But this discharge is not measured as fuel consumption, even though (in normal driving) it would eventually have to be recharged (from energy that ultimately comes from the fuel tank). So a hybrid's city fuel economy may be significantly overestimated by a short drive like on the EPA test.

Consumer Reports magazine does its own fuel economy tests on its test track. It usually gets worse city fuel economy than the EPA, but often better highway fuel economy. Relative to the EPA numbers, manual transmission cars do better than automatic transmission cars in Consumer Reports' tests. Here is the link of their results:

http://www.consumerreports.org/main/con ... 0795808685

Seems that they forgot to note that most of the sporty cars that they tested had manual transmissions.
 

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Re: EPA Mileage "estimates"

tjl said:
Panjandrum said:
I don't know how they come up with these things, but nobody ever seems to get anywhere close to the mileage estimates in any vehicle.
I've beaten the EPA highway number in three different cars, in driving that is about 70% highway. However, all three have (had) manual transmissions and were not hybrids.

Two hypotheses:

1. Manufacturers can tune cars with automatic transmissions to optimize shifting for the EPA test. Considering that the test cycle is well known (to manufacturers) and many of them will do almost anything to get an extra mpg out of the EPA test (low rolling resistance tires, 5W-20 oil, etc. -- even on non-hybrids), it wouldn't be hard to believe that cars with automatic transmissions have shifting points tuned for the EPA test. Manual transmission cars are not so tunable, since the EPA test driver is supposed to shift at specific speeds -- setting the gear ratios for a manual transmission for the EPA test may result in a car annoying to drive. So it is possible that the EPA test overestimates automatic transmission cars but underestimates manual transmission cars.

2. A hybrid starting the EPA test with a full battery may end the test with a partially discharged battery. But this discharge is not measured as fuel consumption, even though (in normal driving) it would eventually have to be recharged (from energy that ultimately comes from the fuel tank). So a hybrid's city fuel economy may be significantly overestimated by a short drive like on the EPA test.

Consumer Reports magazine does its own fuel economy tests on its test track. It usually gets worse city fuel economy than the EPA, but often better highway fuel economy. Relative to the EPA numbers, manual transmission cars do better than automatic transmission cars in Consumer Reports' tests. Here is the link of their results:

http://www.consumerreports.org/main/con ... 0795808685

Seems that they forgot to note that most of the sporty cars that they tested had manual transmissions.

Note: My 2004 Prius is our third Prius. Our first two easily reached or beat the EPA ratings. The 2004 model is very disappointing. We traded in our 2001 model for the 2004. BIG MISTAKE. We have driven both our 2002 and the 2004 Prius cars in parallel on many different short and long distance drives. Contrary to the EPA reports the older model is far superior in all types of driving. I have noticed that the battery range of the newer model rarely moves out of the 40-60% range. The older model used the full capacity of the battery pack, the newer uses only a small percentage. Accordingly the engine runs about 20-35% more often in the 2004 than the 2002 model. Obviously the lesser the battery capacity is used, the more the hybrid operates as a conventional car. The battery pack in the new Prius is the same as the older Prius, but the newer Prius has about 40% more power (primarily due to higher inverter output voltage). I am suspicious that as the battery voltage drops, with the increased power draw, Toyota has experienced battery pack or related failures due to the high voltage draw. I wonder if the original mileage tests were with the battery voltage setpoints (when the engine turns on and off) similar to the original Prius, this would give the substantially higher mpg values. Toyota may have since adjusted the set points to eliminate failures induced by the high amperage at low battery voltage. The solution is a battery pack of higher capacity. Toyota has informed my dealer that a "fix" will be available at the end of summer. I guess we'll see what happens then
 

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Averaged 50mph on my first tank.

I do not drive over 70 on the highway, I dont rapidly accelerate and deaccelerate and keep it or just above the speed limit on local roads. Very very pleased. Just love the way the gas engine shuts off at a complete stop.
 

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Pebble Beach said:
Averaged 50mph on my first tank.

I do not drive over 70 on the highway, I dont rapidly accelerate and deaccelerate and keep it or just above the speed limit on local roads. Very very pleased. Just love the way the gas engine shuts off at a complete stop.
I rarely drive over 65 and drive as you do also. On the highway with cruise control set at 60-65 on the absolute flat (I live east of Sacramento, driving on the flat up or down the valley) I can get 49-51 also. BUT the older model, under the same circumstances would get 60-62 mpg. (note that that with the cruise control set at 55 I can get 66!) Don't get me wrong, I like to new Prius, I, just like every other Prius owner I've talked to who owned the earlier model prior to the 2004, am disappointed. The absolute only reason I traded our 2001 model in on the 2004 was specifically because it was advertised as getting better mpg in all driving situations than the earlier model. This absolutely not the case. A representative from Toyota America in Torrance actually confided to me that his parents had done as I have, traded in their older model for the new one and is getting as poor (everything is relative) gas mpg as me and every one else I've talked to. He felt bad because he had talked his parents into trading their older model which they loved (just like us) for the newer one and they were very unhappy. Note I agree with you that it is pretty neat how the engine turns on and off. However, you need to go and drive one of the older models and you will really be impressed. The engine of my 2001 which we traded in and my 2002 which I still own runs far less often than the 2004. I live in the hills east of Sacramento and my office is only about 2 miles from my home. When warmed up I can drive to or from my office with the old model having the engine run only 1/4 mile up a particularly steep hill. In contrast, under the exact same circumstances with the new model it is impossible to make this same drive without the engine running for at least 1.5 miles of the journey.
According to the Toyota Rep in Torrance, the people who have never owned a Prius before genererally like the new one, those that have owned the earlier models generally don't, this is only because of the mpg issues.
 

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Sorry you are disappointed. Truly

I think the mistake you made (and I dont mean this harshly) was to apparently make a decision about a car solely on gas mileage. One of the primary reasons I got the 2004 Prius rather than the older models was because of size and comfort. There are some other reasons as well. Apparently those reasons were not there for you, so it seems mpg was the only reason you switched.

I definitely love the idea of driving an environmentally friendly car and that was a key part of my decision. Would I like to get 60mpg or more? Sure. But am happy with what I am getting and would not switch in a few years over the promise of more mpg unless there were other benefits as well.

Again I am sorry for your experience, perhaps you can sell it and buy an older model?
 
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