Why mpg testing is difficult and variable...

[ZugyNA]

There are many variations on the approaches to engine and fuel management design by engineers from many different cultures...the only common ground in the US being the fuel used and the EPA emissions regs.

Also each vehicle might have a different total mileage and state of tune....and possibly other modifications from stock.

So a modification that might increase mpg on one vehicle...won't necessarily have the same effect on another.

So this might be why using an A-B-A testing method with statistical analysis might be a kind of overkill. Though with a good mpg readout method and a good test route...that might not be so relative to one particular car.

Main point is: even if you do careful testing of a mod on one car and find it doesn't increase mpg...that doesn't mean this mod might not work on another car.

1) you might not have set it up right...the devil is in the details?

2) this kind of mod just might not work on this particular car?

So...to try and extrapolate from testing an mpg mod on one car to all cars...is NOT statistically acceptable?