I'm starting my 3rd tank of gas, and there seems to be about a 2 MPG difference between the display readings and my calculated MPG (the display is consistently higher).

Are other people seeing a similar difference?

Does anyone know if there's a way to 'zero' the gauge properly?

No problem for me.

Mine seems to be accurate.

The way this works - I think - is that the computer for the fuel injection measures how much fuel is being metered into the engine which then compares this amount with distance the car has traveled. If the engine is running properly then you would think this would be fairly accurate but I've seen other complaints. There could be a lot of variables with doing your own calculations such as temperarture, the pump at the gas station, how consistent you fill your tank to the same level, etc.

My MPG meter is only off by a 10th or two. I don't think it takes overfilling into account.

What is way off in my car is the mileage countdown. It always starts at 599 and tells me I'm out of gas when I still have four gallons (140 miles) left. I could understand a 50-mile buffer but 140 is a little much.

Yup, same issue. The compromise I've reached for myself is that I plan on refueling at about 550 miles. Even then I always have at least 2 gallons left.

Yes, my 'Range' display is conservative too. It always wants me to fill up when I've got about 3 gallons left.

That's not all that different from my last car (3 gallon reserve out of 20, vs. a 2.5 gallon reserve out of a 15 gallon tank), but there's a big difference in how far you can go on that reserve gas (100+ miles in the NAH, vs. 50+ in the old car).

I agree, there's a significant measurement uncertainty with the manual calculations, and that may be all that I'm seeing. If it averages out over more tanks, then there's no problem.

But a 2 MPG (5%) difference seems a bit too much to explain that way, and it strikes me as odd that it is consistently off by the same amount and in the same direction (so far - 2 tanks is not enough for reliable stats). To me, that suggests that the gauge is not correctly zeroed.

Mine is WAY off. It will read 33.6 MPG constantly... and then when I calculate the tank it is 35-36 MPG every time. It seems to read 2-3 miles low, but I'd rather have it read low than high. It's always a fun surprise to get the real MPG when you calculate a tank.

What I do find interesting is how the summer weather dropped the MPG meter. It used to read 34.9 or so all the time... and then summer hit and it went to the 33s and stayed there.

Are you all resetting your mileage computer at each tank or are you letting it go so it shows your lifetime average?

Do any of you reset it at each trip?

Do any of you know if the NAH computer bases any of it's calculations on the "Trip B" counter like some of the other hybrids do?

My mileage improved in the summer from 34-35 to 36-37 MPG.

I reset the MPG display when I fill the tank. So far, I've kept 'Trip A' and 'Trip B' the same (also reset at each tank), so I don't know if any of the other display calculations are affected by it. I suspect that they aren't, however, since most of them can be reset separately.

For the mileage on individual trips, I calculate that from the change in the display mileage (and the distance driven).