Chevy Cruze got 72 mpg for one commuter

[RAMd®d]

QFE, the original statement is BS.

Agreed.

The only real exception is the deliberate tampering with pumps by the station to bilk customers. It happens, but I don't know to what degree.

[Mini 9]

They are not very accurate. Just spend some time with the Fuel Economy nerds on those sites. Counting the times the fuel injector cycles, which is how the Prius does it, is likely more accurate over the long haul than all the various pumps your car visits throughout its life. But no skin off my teeth.

[JoeH]

The calculation done to get a mpg figure by counting injector cycles has a big source of error, a built-in assumption on the exact volume injected. However, the engine control computer does not actually depend on an exact amount, it uses the various sensors to adjust the number (and in some systems, length) of cycles to meet the programmed power and pollution requirements. Through its feedback loops each computer gets the right amounts for the engine and injectors, and adjusts them as wear occurs.

The gas pumps have a better accuracy because they are designed from the beginning to measure an accurate volume flow. The states also have a vested interest in keeping them accurate, it is how they collect a bunch of tax revenue. The in-car displays would need to be using an accurate flow meter coupled with the odometer instead of inferring a flow indirectly to get a really accurate result.

[RAMd®d]

They are not very accurate.

Not true.

[Mini 9]

Are so.

[JoeH]

Mini 9 wrote:
Are so.

For "no skin off my teeth" you are somewhat invested in your position. But just because you got some info from some "Fuel Economy nerds" does not mean it is accurate.

Straight from one auto manufacturer the accuracy of their mpg displays was given as +/- 5%, and that any accurate measure would come from calculating it based on gas pumped into the tank and mileage. To get an even more accurate number would take several tank refills to even out the variance caused by different gas nozzles cutting off at varying full levels.