EPA asks Toyota to lower fuel economy estimates for hybrids

ya that is the problem... 15% error means going from 15 to 13 mpg in a SUV and why bother? hardly a change really... but in a Prius that same 15 % lowers the mpg from 55 to 46....seems like a lot more eh??

but lets face it, its just those manufacturers of gas guzzlers that are asking toyota to falsify the results of their EPA testing.

its like i said... ineffective damage control.

 

response to Davein OLY WA

<div class='quotetop'>QUOTE(DaveinOlyWA\";p=\"38726)</div>

Maybe I'm missing something here or having a senior moment...but, Dave, if your readout tells you that you have gone 200 miles and the MFD shows 55 mpg, that means you have used 3.64 gallons of gas to go 200 miles. I don't know where you get "50 miles on 0.64 gallons for an mpg of 78.13 mpg". You can't divide the trip into segments like you did, unless you reset the ODO at the end of each segment. The computer takes the total miles driven from the time you reset the ODO trip function, and calculates the fuel burn average as you drive. This is why your miles per gallon look great after the first half hour of driving, and continue to look good for the first hundred miles or so, but the little side trips of less than 15 minutes when the engine does not reach optimum temps will eat into your average.
For example: You fill your tank, set your trip ODO to zero and start off.
Initially, as we all know, your mileage sucks for the first five or ten minutes, or the first two columns on the bar graph display. Then, as you continue driving without shutting the engine down, you can get the mileage upto the mid 50's in normal driving. If every trip youtake is at least 20 minutes in duration and more than 15 miles, you could reset your ODO at the beginning of each trip, and have a cumulative average mpg of mid 50's or even better.
If, however, you don't reset the ODO, the averaging works against you because there are a greater number of miles driven for the computer to average in. So, if you are driving smoothly for 150 miles, then change your driving so that your instant readout is showing much higher mpg, i.e., you've been driving slowly in city traffic, etc, that new higher mpg has to be averaged against a greater number ot total miles, so the effect of having a short term higher mpg takes longer to actually change the mpg readout.
Confused?
Bob

 

<div class='quotetop'>QUOTE(DaveinOlyWA\";p=\"38726)</div>

Like you, I find the computer to be pretty accurate. In a typical month, I'll put in about half a dozen tankfuls, and it's always turned out to be within about 0.5 mpg of calculated. Per-tank, there's noticeable variation; I believe it's the inconsistency of fill that causes this.

Anyway, the point of this post is to ask if you take account of the accuracy of your calculation. The display resolution means it's possible to be out by ±1 mile in your subtraction and by ±0.1mpg, so perhaps your initial mpg was almost 50.1 and you finished at almost 201 miles - you would have done only 51 miles on 0.66 gallons for an average of 77.21mpg.

Alternatively, you might have done 49 miles on 0.61 gallons for 80.36mpg.

That's at a ratio of 3 old miles to 1 new mile. When you get nearer to the end of the tank, the error margin goes up a lot, particularly for short trips. (For a comparison, imagine going from 50mpg at 450 miles to 55mpg at 500 miles - the error range is ±250mpg!)

 

i use trip A for tank calculations so the error is .1 mpg