dougm213

Anyone else noticed the computer vs trip computer mileage is consistently different? I still use the old fashion way of calculating MPG. Mileage since last fill-up/Gallons. I have consistently calculated 1.5 to 2 MPG over what the car computer calculates. This is over at least 15 fill-ups and I go two hose bump offs past first kick-off when refueling. I can understand if it was a few fill-ups but this is consistent over many tank fill-ups.

On another note, on highway, warmer weather, in normal mode, non-aggressive, I get 25 to 27 MPGs depending on how many hills I encounter.

And just to avoid the wise responses, yes, I know how to do division, sometimes I even use my toes.

Christobol

I've noticed that my since refill vs resetting the calc doesn't match. I've also noticed that if I push the mileage rather than refilling when I get a low tank warning the mileage calculator starts climbing.

georgee01

With the GS hybrid, I find the the computed MPG is consistently 5-6% higher than the manual calculation at the pump.

AL13NV8D3R

This sounds just about right I average about 25mpg in a tank of gas whether manually calculated or off of the car computer.

suprajjang

iTrader: (1)

I agree with the OP. So far I have gotten about 2mpg higher calculating the old fashioned way compared to the computer.

krawfo

I was just going to start a thread with this same topic. I've only checked once but my calculated MPG was about 2 mpg greater than the Since Last Fill Up showed. I guess they figure that no one is going to complain about getting better mileage than what the computer shows.

jjscsix

You folks don't think the cars computer is wrong, but you assume that the odometer is accurate and you are filling the gas to exactly the same level every time?

georgee01

The pump calculation is not accurate for a single fill-up due to the differences in shut-off levels from pump to pump. If you keep logs, that will average out over time, giving you an accurate number. I've filled my GSh up 10 times, so I've got pretty good data.

As for the the computed MPG, you have the two numbers, Average, and Since Last Fill-up. My observation is that the Average seems to be a moving average, which you can reset. I have to take the Since Last Fill-up for what it says it is. With my GSh, both computed MPG numbers are 1-2 MPG higher than my calculation at the pump.

dougm213

Where would the computer get number of miles for its calculation, does it maintain a different miles count than the odometer? I would think it is the same number. If the odometer is wrong by .1/10th of 1% then I would think the computer is using the miles that is also off by the same fraction.

The question is how does the computer calculate the number of gallons used? Where is that number coming from? I am not a physics expert, so can't tell you is temperature or other factors impact volume of the fuel tank.

I always fill it up, but how does the computer react to partial fill-ups?

As mentioned by the previous poster, my calculations is over at least 15 fill-ups. And consistently it is 1.5 to 2 MPG off. I am assuming the discrepancy is accounted for by "filling the gas to exactly the same level" which is unlikely.