Will there ever be a fix for the MPG estimates?

This subject has been gone over in several threads last year and especially in 2009 when the 2010 Prius was newly released. I belive that they have left it reading higher than what most of us get in actual measurement on purpose. It makes the average operator that is not into detailed records feel good. Thus they can say positive things to their friends about their prius. In a span of 18 months ours has varied from 3% to 6% higher than actual. I can not complain as our lifetime average is still over 52mpg. The computer reading 55.1 since we got the 2010 Prius

 

Displayed speedometer and odometer errors should be different, and mine are. While my speedo reads slightly high, my odo reads a fraction of a percent low (0.2-0.3%), or at least it did when the tires were new.

Speedometers are biased high due to various government regulations, something about not giving drivers an excuse for speeding.

Odometers are (or soon will be) biased low due to class action lawsuits about warranty fraud, such as those that hit my previous car brands (Honda and Subaru). I believe both settled by giving a 2% odometer extension on the warranties.

 

Regardless of odometer accuracy, couldn't the displayed mpg, presumably calculated with the displayed mileage, more closely mirror calculated mpg, also calculated with the diplayed mileage.

Geesh, I'm not sure if I understand that myself, getting tired

 

^^ I believe Gen2 proved that it could.

 

The federal government sets these numbers - not Toyota or any auto maker. They use the exact same parameters when measuring fuel economy in every auto.

So - don't take ANY auto's predicted mpg seriously - there are way too many variables! This number is really for comparisons only - and it works great in its designed capacity.

As already stated, your mileage may (will!) vary.

-Brad

 

With the possibility of out of spec pumps (which might be the least likely since someone at least checks them once in a while and there is a fine possible), and the obvious problems with always filling the tank to the exact same place, who is so sure that the personally computed numbers are any more reliable than the car computed ones?

Besides, what possible difference could it make? It is only a number that really doesn't matter, does it?

 

Our Honda Civic Hybrid underestimated mpg. If it said 5.0 liter/100km, calculated would be 4.8~4.9. Very consistantly.

Our Prius, in the few tanks I've calculated, consistantly overestimates: if it said 5.0, calculated is 5.3~5.4. Roughly double the inaccuracy, to the optimistic side.

I'm sure a patch could fix this.

 

MPG gauges have inherent inaccuracies.
Get over it.

 

I forever a pessimist, believing that Toyota intentionally allows MPG's to reader slightly higher than actual. Of course, the only real way to calculate MPG is to do it manually and even that may be skewed by pump error.

The other possibility for MPG errors may be differences in fuel mixtures from the pump's supplier; i.e. ethanol percentages, water, octane inconsistencies, etc. I would think these issues could influence actual MPG readings across multiple fill-ups. Last but not least, let's not discount warm/cold engine consumption, road contitions, blah, blah, blah...


Happy Motoring,

Tom

 

Yes, this much error in the pump is a violation state weights and measures laws

This is a problem only for single refills. When combining fifty consecutive tanks, the probable error becomes tiny.

Having checked the odometer too, I am quite sure.

I'll guess that you are not an engineer or accountant.

 

The EPA figures seem correct for my V. I was averaging 54 mpg until the recent blast of cold weather reduced it to about 51 mpg. At the pump.

 

You are driving one of the most fuel efficient cars in the WORLD...
why are you even letting the few mpg inaccuracy bother you.

just my .02

 

My difference between displayed MPG and calculated has been a steady average of 3.3 mpg for about 18 months now. It is up and down between tank refills but the average has remained fairly consistent.

I really would like for Toyota to fix this issue. I automatically subtract the 3.3 mpg from the display number but would much prefer for the display to be reasonably accurate.

 

Some of us don't appreciate Toyota intentionally having a 5% optimistic error in the system. an error that they could easily take out.

 

I agree Toyota should correct this discrepancy.

However, I believe short fillups, say under 150 miles, may be more
consistently accurate.

alfon

 

Every vehicle I've owned that had a computer mpg indicator has always been off to the high side. It's seems more so in the Prius because a 6% difference is numerically higher (3.5 mpg difference) due to it's high mpg rating than a vehicle rated at 20 mpg (1.2 mpg difference). What is reasonable accurate for you?

 

not that much of a big deal, though would like adjustment to miles to empty... I have never put close to 10 gallons in the tank, including a 530 mile trex

 

Reasonably accurate to me would be +/- 1 MPG.

From posts by the Gen II owners, the Gen II seemed to be much closer than the Gen III. Within what I would consider reasonable. This was apparrently a marketing ploy by Toyota.

 

Mine seems about 5%, really surprising actually that such a huge error in this direction is noted by all of us. They simply calibrated the calculations incorrectly.