If I remember right I think MythBusters found that it was acutally the car with Windows up Airconditioner on had slightly better milage, I don't remember but I will have to try to see that epesoide again!

 

That is correct. And don't forget with the windows down, your car is act as a paracute, kind of.

 

Another controversial topic...
However, I recently read an article on this from a reputed mechanic.
Octane rating has nothing to do with mixture richness! Octane affects the speed at which gasoline vapor burns. Low octane means shorter explosions, while high octane means longer, controlled explosions, and therefore less knocking.
Most engines nowadays are made to burn 87 grade and sometimes less. Running on 94 means expensive exhaust gases! In no way using high octane can improve gas consumption in an engine tuned to use low grade gasoline. Sensors vary the timing and retard it when knocks are detected. High octane means no knocking are no timing adjustments. That's it!
So, instead of contributing to the already outrageous profits of oil companies buying expensive high-octane gasoline, you may spend your hard earned cash on something else. Unless your engine knocks badly on 87, of course.

For the windows v. A/C thing, open windows at high speed makes your car act like a big whistle and increases considerably the drag effect.

Happy driving!

F.

 

I always use at least 89 octane gas, sometimes i "think" i can tell the difference. But whether the 89 is mechanically better than the 87, i have no idea!
However, i do seem to get better gas mileage on 89, like 3-5mpg or beter than with 87 octane.

 

New spark plugs and wires will make a difference in MPG as well as inflating your tires a few pounds higher than what the owner's manual recommends (don't exceed the max. pressure listed on the sidewall, however)

Dusty