MPG Calculation Accuracy

[GChamb]

Very often I find that different pumps will fill up my tank to different levels. If I calculate my mpg manually and come up with a low mpg average, on average the very next time I calculate at fill up it will come up high. If I divide the two it comes up to what my fcd shows. Trust the fcd!

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[olrowdy01]

Originally Posted by Need4Speed

My gas calculations are usually very close to what the display shows. Typically the display is less than 2% off from what I calculate. My calculations are typically a little lower than the fcd, but sometimes the fcd is slightly lower. I have also read that temperature affects the actual amount of gas, that the pumps are calculated at a given temp (72?). I believe I read an article that people in Canada have complained that ov a year time frame the average temp is less than the cal temp, so in the long run they are getting jipped. People in warm states might be getting more than they are paying for.

If I remember correctly about the USA pumps, the oil companies said it would cost too much to put the temperature compensated pumps in.

Except in Hawaii, where I think the state demanded they put them in and it wasn't too much to do.

[Eli]

On average, the FCD is accurate to within 1%. But it can swing as much as like 8%.

For me, at least.

[dandism]

I just re-fueled. The FCD showed 58.9mpg, but my calculation showed 55.4 (for almost an entire tank)

[RedDawn]

Just did my first full tank in the car: display showed 57.1, fillup calculation added up to 57.0958.

[samwichse]

I've tracked the FCD in my HCH1 over 21000 miles now (every fill up, actual mpg and the displayed FCD recorded).

The result: The FCD is actual MPG + 1.99.

I also tracked my I1 the same way over 36000 miles.

The FCD was actual mileage + 1.08.

Sam