Quote:
Originally Posted by TheSpoils
Do you have a definite understanding as to why the hand calculations only match the display occasionally and / or why they tend to always be less than the mpg computer display?
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From the prior discussion, there were a few people whose MPG display read consistently low, but most were high.
On my car, the odometer is about 2.5% low (by highway survey markers), and the MPG display averages 7% higher than hand calculation (over more than 10 tanks). Those two calibration errors partially cancel out, so the MPG display is really about 4% high overall. I really don't expect the instruments to be any better calibrated than that, so there's no great mystery.
That said, I still think the MPG display is far more reliable than the hand calculation on any one tank. There's a lot of "noise" in my hand calculated numbers, depending on just how well I topped off the last tank.