Ah, yes, the Internet. A great place for information, but a great place for rumor, happenstance and conspiracy to run around the world before truth has a chance to get its pants on, to borrow from Winston Churchill.
Yup...warming up the fuel in EFI system?? come on folks! YOu'll get vapour lock in heatsoaked carb back in the 70s if the fuel is too hot, now try that on EFI? (note: EFI systems doesn't care about your fuel temperature at all, everything is properly adjusted/compensated by the computer under closed-loop operation. Latest generation of EFI designs, computer will store various different detected readings from various different sensors for future referencing/minute adjustments (that's intelligent!)...
what next? tin foil antenna to facilitate aerodynamics? squirting water in front of the tires (all 4 of them) to lower friction coefficient further to increase mileage?? gimme a break...
No kidding. How mant AT are slipping and burnt up because of this? The only thing that may increase mileage is drawing in hot air instead of cold. The comupter will compensate for less dense air but of course less O2 also means less power(poor trade) and it won't work unless you're just puddling around. I wonder how much gas that 20w50 will save me in my 3.0 Mazda/Ford.