Increasing Gas Mileage With Taller Tires? Options

[joyworks]

One of the few things that I dislike about my '99 Celica Convertible is that the gas mileage isn't as good as it could be. The 1997-2001 Camry, which had the same engine, got 3 mpg better on the highway with a 5-speed than my Celica does with a 5-speed, and the Camry weighed about 300 lbs more! I can only attribute this to the high revs of my Celica's 5th gear. So, my question is, can I achieve better fuel economy with a larger diameter wheel/tire combination? I know it would throw my speedometer off a bit, but to save fuel, it would be worth it to me. On that same note, what would would the tallest tire that I could put on a 16" rim and not suffer from any fender rubbing? What about a 17" rim? Thanks for your help!

[97GTinKC]

Wheel size alone can not be used as an indicator of weight. It all depends on the particular design, and there are better and worse ones out there. I would bet you can find 18" wheels with low profile tires that will weigh considerably less than the same overall height/width combo in a 15 or 16" wheel.

I am pretty sure you would gain fuel mileage with taller tires in a GT, (maybe not an ST) there is plenty of power available at highway speeds, I keep thinking I need another gear. But keep in mind- if you do change, it will throw your speedometer off so you may not be able to accurately calculate the actual gains.

My own mileage has dropped from a constant 29.9 mpg average to 27.5 ever since Missouri forced ethanol on us. This is what happens when you get government involved in technical/economic stuff. If I am adding 10% ethanol to the fuel and my mileage drops by 10%, I am burning the EXACT SAME amount of gasoline + the ethanol, so what have we gained in carbon emissions or oil usage reductions except to now drive up the price of food also?