Warnning: MPG gauge meter is inaccurate for all prius

Yup, so your first calc will be off a little, to one side. And the next will be off to the other way, cancelling out.

Say on your first fill up you got the tank a little fuller than usual, and this is reflected in your calc, "dropping" your mpg. With your next fill up, it'll take less than usual at fillup, "improving" the mpg. And by now your running average will be pretty deadly. And these variations are small to begin with. The longer you record distance travelled and gas consumed, the less anything can budge it.

 

It might be negligible, but that doesn't change the fact that it's still there. I understand that it's there and use fuelly as well (love it). But I understand that these things are all outside of my realm of control. I deal with it and move along. I was just pointing out that they are there and that the computer might not be as inaccurate as everyone thinks.

 

If pump a puts in 5.5 gallons out of 6 and pump b puts in 5.3 out of 6... I can't just "assume" that they will cancel out. They will be close, I'm not disputing that. I'm just saying that there will still be variation.

 

Why would I need to find an excuse for an inaccurate meter? I am smart enough to believe that with today's technology Toyota could install a computer to alter the mpg readings by 1% or whatever they wanted. In fact it would be easy enough for them to put one in that the driver could adjust under settings. I think it is stupid to think otherwise, and if I want to complain about it I will.

 

I just minus the 3+ mpg off what the meter shows while driving - it's automatic by now.

Fuelly tells me what I need to know for the record.

YMMV

 

Can the C be improved? Absolutely. What car can't?
I must have missed those in the 2nd group. But then it's been a while since I went back and re-read all 4 pages.

 

The meter and fuel nozzles at stations can affect the gauge, though. It won't be extreme and someone who isn't doing experiment level notations will never notice it, but it's still there.

 

I agree the meter is set wrong. and that must be intentional from toyota.

 

Since the meter reads how much fuel is being burned... from the tank... it does have a correlation. Just like all of the others that I mentioned, but whatever the cause, they do still all add up to the meter being wrong and that shouldn't happen with today's tech.

 

5% on a 50mpg car is the only reason you notice it. They probably* wrote the code on their first gauge (which would have been around a 25mpg car or even less. At 25mpg you are looking at the car telling you that you are at 25 when you are really at 24. They probably* figured that it was close enough and worked, so why fix it.

*probably is being used because I don't work for Toyota, I just use the logic that if they wanted to lie about something, they would do it like Ford did and lie completely. The car gets what the EPA test says it will (which is what Toyota says the car will do)... and then some, in most cases.

 

And now you KNOW what the fudge factor IS and yet you still ALLOW it to upset you.
That is YOUR problem; not a problem with the car or with Toyota.
YOU just need to get over it and move on.......to something that is really important.

 

Frankly, if this is the greatest tragedy in your life I hope you count yourself very blessed.

 

My 2013 Prius C has shown a consistent deviation between the displayed fuel economy and the fuel economy measured by mileage and fuel volume. Summer through fall, the two match very well. In WINTER, the deviation correlates with temperature: the colder it gets, the more the display over-estimates the actual fuel economy.

Maximum deviation during the coldest months was about 10%.

Fuel dispensed at the fuel pump is measured by a "for trade" traceable measurement device corrected to 15 C, here in Canada at least. And unlike my 2008 base model Prius, there is no tank bladder to confuse fill-up to fill-up economy checking by introducing a variable tank volume to "full". My 2008 averaged 5.77 L/100 km over 190,000 km, start to finish, and my 2013 Prius C is doing better than that, so I'm not concerned. Just curious about what might be causing the deviation that increases as the ambient temperature drops. It's not fuel density, as that would work in the other direction. It's not air density or temperature because air mass flow is measured by means of an actual massflow measurement device in the engine. Very curious what the issue might be...it is definitely there.

 

You're the first one I've read about that is having a temperature based variation. The rest have been consistently 3-5% off.

 

mine is less than 2% off over the lifetime. Thats less than 1 mpg off getting over 50 mpg calculated at the pump.

 

That's excellent. But it's consistent right?