Im new to this site and was wondering the best way to check miles per gallon. Right now I am letting the gas nozzel shut off by its self and divide gallons into miles. Is this correct?
Yes, your math is correct. And you are correct to be consistent where you let it shut off for each tank. You will see some variation from station to station but over time this will average out if you keep up with your mpg per tankful. My displayed mpg on the MID is high by about 6% or about 3 mpg compared to my calculated mpg at the pump. This is consistent with most others on here.
Most of us who have computed our mileage over several thousand miles have found the Cons display for Trip A and B will read consistently high by about 4% to 6% as mentioned by JD. I believe most of the people who report their mileage on this forum use the Cons mileage. So if you find your computed (miles/gallons) is a little lower than others are reporting that may be why. If you subtract the built in error the Cons readout seems quite accurate, at least I have found it so.
My MFD error is very close to 6%. I mostly use the same gas station and the error is very consistent. I never "top off", which is bad for many other reasons anyways. If you average over several tanks, the variation in the shut off point of the nozzle will cancel out. Reset Trip Meter (or note odometer) after each fill-up. Real/Calc'd MPG = Miles Driven under last tank / Gallons Pumped to Fill Tank
What matters to me is that the MFD provides information that allows me to adjust my driving to maximize MPG. The odometer reading is not perfectly valid and I don't care about MPG bragging rights. As long as the small difference between the MFD and odometer miles divided by fill gallons remains relatively constant (+3% to +5% or so), the Prius MFD provides precisely the information that I need to adjust my driving. Enjoy your car and use the MFD to balance your driving habits for fuel economy or the occasional need for speed. My guess is that you will continue to use the MFD to get excellent mileage and to fill the gas tank in your Prius when it approaches empty, regardless of how you estimate MPG.
Some would go so far as to say use the same pump at the same station using the same "notch" when filling it. That is what I do.
There's an implied concern in your question that pump technique will make a difference to your calculations. It will, but only for one tank. If you're calc is low one time, it will likely be high the next time. By 3 tank ups any inaccuracy should have cancelled out. I agree also with the mention above: once you know the approximate error of the in-dash display of mileage, you could just rely on that, factoring in the error, for a rough calc. It would be nice though, if Toyota would fix this, say with a software update. It can be done, there is no excuse not to. Honda, for one, has slightly pessimistic in-dash display of mpg.
If the 2011 has a bladder like my 2009 then I had to top it off to re-expand a collapsed bladder that would only take 3 gals. ARGH
Unfortunately I don't think they ever will. It appears to be a marketing decision so people will think they are getting better mileage than they are. Apparently Toyota management doesn't realize that some of their customers can divide distance by quantity and come up with the correct answer.
It makes me think of when you know someone, who constantly BS's. You adjust to it, learn to deduct the BS factor, but it's frustrating.
Yeah, you are absolutely correct. However, the automakers know that 99% of the people don't do the actual calculation.
