Your local gas station probably offers you 3 levels of gasoline, like
> gold, silver and bronze. These typically have different levels of
> octane in them and you will generally get a little better mileage for
> the more expensive type.
Higher octane gas NOT get you better mileage. Use the octane rating that is suggested for your car - no lower, no higher.
Using high octance gas in a low octane engine is a waste of money. Using low octane gas in a high octane engine will cause detonation and damage, or cause the computer to adjust timing and waste power.