2010 Toyota Prius FCD Inaccuracy

i dont think its a conscious deception on Toyota's part. they simply made an error in the algorithm used to calculate the mileage and is (i hope) slow to fix it.

also, Shawn; i dream of times when my tank is "only" 5 % off. its usually much more than that for me. it seems the higher the display mileage, the farther off the real mileage is...it seems like after a certain point, i am on a "2 for 1" system where i need 2 more MPG's on the display to get one real MPG of improvement

 

Dave, fill volumes are more variable, but they have nothing to do with actual fuel mileage. (Putting in fewer gallons in a given fill--intentional or not--does not change the actual fuel mileage.) The problem with the 2010 FCD is that it is misrepresenting the actual mileage to the customer...as well as potential customers. If there is documentation trail that Toyota is aware of the bias or did it intentionally, then it constitutes fraud.

 

Considering the reports here and at CleanMPG, it seems like a planned method to get the early MPG reports to show outstanding mileage. The pattern of early builds having the largest discrepency and now cars showing almost none as sales have taken root!!!

 

not talking about fill volumes. its the difference between MFD mileage and displayed mileage. with no bladder, the ability to fill to a consistent level should be fairly easy to do and that has proven the case in nearly all my tanks.

 

that i have also noticed with many who got theirs in like August or September only reporting differences of 3-4%. am i to think i got a "bleeding edge" car? if that is the case, that makes it worse that we are not afforded to opportunity or at least the option to have our software updated.

my LT average is MORE THAN TEN % higher on MFD than real mileage.

some here think 5% is bad... well, i wouldnt mind that right now

 

I try to give Toyota the benefit of a doubt as I think they deserve it for the most part.... however there have been a few decisions they have done that have made me question.

Nevertheless, for some a fine tuned complex car that accomplishes a marvelous feat, I just can't believe the engineers would "miscalculate" such a simple calculation that carries some a highly charged political and marketing impact.

I agree... I can live with non perfect calculations which would account for sometimes too much and sometimes too little, but when the sights on my Gun consistently errs to the left, I start to think the sights are off and need adjusting... but when it bounces to the right and the left, then its something else.

I could say "well since its no longer a flexible container, it threw them off" but this is not rocket science for such an accomplished team of engineers....

 

Yep. Looks intentional, particularly with Toyota's denial of there being a problem that is obvious to everyone else. If they had identified an actual error and corrected it, then it would have been easy enough to identify the issue and even delay early adopters with a "we are working on a fix for existing vehicles, be patient" statement.

 

well, maybe this electronic efficiency counter inaccuracy is not a Toyota exclusive.

on another thread talking about the Honda Insight there is a link to an article about the Insight getting 60 mpg...

here is a post from one Insight owner

I consistently get 44 mpg on a freeway/city cycle. I'v never seen anything close to 40 or 60. That's doing it the right way, by filling with gas and dividing into miles traveled since last fillup, not the fictitious dashboard mpg indication. How are you people getting these crazy numbers?

 

Between 40 and 50 mpg my car is 2 to 3.4 mpg over actual calculated mpg

 

What will we be asking them to do with our complaint?..

 

That was probably me. Seems my original complaint got lost. Heather did say they talked to my dealer and confirmed my complaint is legitimate and they are working on a fix. Maybe I should take a drive to Torrence and show the tech group the problem since they seem to have a hard time coming up with a fix.

Wayne

 

Toyota need to face it that the MPG guage off according to at least hundreds of 2010 Prius owners.

Perhaps we could have class action suit if they do not correct the problem.

It is clear to me that with nearly 15,000 miles on our Prius the MPG guage off by 2 to 4 MPG, sometimes higher.

alfon

 

Count me out of any class action lawsuits over this issue. I have not been damaged in any way, shape or form by the indicator being off a few MPGs. The car was marketed and I bought it based on EPA fuel economy tests, with all their strengths and flaws, just like every other car sold in the USA, not the reading of some internal computer. My Honda CR-V indicator is off too; should I sue them also?

 

thats kinda my feelings too.. the Prius is so perfect is so many ways, Its easy to expect everything to also be perfect forgetting that most other cars can't hold a candle to the complexity and fine tuned efficiency of the Prius.

2.5 mpg off of 50mpg is only a 5% aberration.

That same aberration in a car that only gets 25mpg would mean it would have to be off by 10% to match the same loss in gas mileage. (2.5 miles in one gallon)

In light of all thing the things Toyota has been forthright about, I can give them a little grace.

However, there is talk that this was a pre-meditated deception for marketing reasons.

While I have faith that the expertise of the Toyota Engineers should be able to nail this one perfect as this is not rocket science, I'm not upset about it as I really like all the rest of the car and its no big deal to me.... especially if the problem is consistent.

Many guages are off on many cars.... but its just a calibration issue as long as they are consistent, the quality is still there, otherwise... no one claimed the instruments were fit for a Jet Airliner.

Toyota could offer to recalibrate the readout, but I don't think anyone is going to be able to hold their feet to the fire legally claiming they have to be any more perfect on their readout than they already are.

A certain amount of tolerance is allowed by the courts and Toyota may know this and may have purposely exercised this grace to the limit.

Good luck fighting their lawyers.

 

ok, so the calculated mpg guage is a little off... i have a bigger issue with the outside temperature thermometer, i don't think it's right. and i read here on priuschat that when you wash your car it stops working for a few days...

 

I've never had that happen and I do my own washes as well as the high pressure touchless washes that get the undercarriage too.

 

Now, if the FCD were more conservative, saying 50 mpg when you were actually
getting 52mpg, would that be a problem? Would Prius owners be storming the castle for this?
Get a life!

 

There is no regulation of industry standard about the fuel economy displayed numbers, therefore we have no chance to win the class action suit, I believe.

There is the UN/ECE Regulation No. 39 about the speedometer readings.
The car manufacturers are allowed to display up to 10%+6km/h above the actual speed.

There are a lot of variables to display fuel economy number, and the accuracies are different between vehicles.
For example, the fuel flow rate of fuel injectors are varied up to a few %.
In the car racing world, people buy expensive, calibrated and matched fuel injectors within 1% variances.

I think the 5% variance of the fuel economy number is not a big deal.
My experience on the VW GOLF was 10% error.
If one would like to record an accurate fuel economy number, one could calibrate the accuracy on one's own Prius, then one could keep track own fuel economy database.

Ken@Japan

 

so it seems the inaccuracies of the speedometers (more inaccurate at lower speeds) and possible inaccuracies with the odometer would explain the variance with the calculated MPGs?

is the inaccuracy so bad that priuschat wants toyota to issue a recall or sue them for some class action suit?