2010 Toyota Prius FCD Inaccuracy

[basspro]

After four full tanks, I am getting a difference of about 4 to 6 MPG higher showing on the MID vs actual pump measurements.

[Sho-Bud]

Trust me, most fuel stations aren't honest. I know a few good ones which allways give me a calculated fuel consumption that is equal to the board computer. I know may that each time you fill up, give you a worse calculated average. It's not the Prius's computer.

[jay_man2]

Originally Posted by Sho-Bud

Trust me, most fuel stations aren't honest. I know a few good ones which allways give me a calculated fuel consumption that is equal to the board computer. I know may that each time you fill up, give you a worse calculated average. It's not the Prius's computer.

Around here the pumps are measured for accuracy by the government on a yearly or semi-yearly basis. It's the computer.

[anne1965]

Sho-Bud,

This thread is about the Gen III.

You drive a Gen II Prius. That didn't have a FCD problem. I think it underestimated by 0.1 l/100 or 2-3%.

I'm only on my second Gen III tank and I don't know how full the first tank was delivered by the garage. Real consumption vs computed was 3.9 and 4.27 l/100 km resp. After emptying my 2nd tank I can say more.

[ken1784]

Originally Posted by EZW1

The error between calculated and indicated on my '09 seems to follow the same trend.

Our observation is 2% accuracy on the Gen2 and 5% on the Gen3.

Ken@Japan

[cossie1600]

The rental 08 I had was always off 5mpg. After one tank, my 2010 seems to be within 1mpg. But then seriously, does it really make that much of a difference.

[msirach]

I just filled ours again. My wife drove this tank and here are the results:
4950 miles
487 miles @ 54.4 fcd
48.68 MPG calculated for a difference of 5.72 MPG or 10.625%

[a priori]

Originally Posted by msirach

I just filled ours again. My wife drove this tank and here are the results:
4950 miles
487 miles @ 54.4 fcd
48.68 MPG calculated for a difference of 5.72 MPG or 10.625%

What is the lifetime difference now?

My most recent fill-up was at 4,999 miles
503.8 miles @ 61.3 (on the MID)
58.4 MPG calculated for a difference of 2.9 MPG or 5.0%
Lifetime at 4,999: 57.0 on MID and 54.3 calculated for a difference of 2.7 MPG or 5.0%

[msirach]

Prior tanks are on a pc at home. I am away for a few days and will post the tally when I return.

[DaveinOlyWA]

Originally Posted by msirach

We have about 4500 miles on ours and on every tank the hand calculated MPG is off 3 to 7 MPG from what the FCD reads.

5 to 10% is out of the box for error. I fill up at the same station, same pump, same number of clicks, and same direction each time with the exception of the fill in Madison last week of which I estimated slope to be the same at the station I filled at.

glad its not only me...check my sig...last tank difference was 8 MPG...

Originally Posted by tumbleweed

Have either of you checked the speedometer mileage against a portable GPS? I wonder if it is the distance, the fuel flow, or both that's off? A gas pump could be off by quite a few percent but I doubt all of them are.

several times. using 2 different GPS systems, no real differences. over 30 miles one system was .2 miles off, the other dead on.