[Sugarphreak]

I have a theory that if you run a larger diameter tire it will dramatically impact your mileage on the highway.

3500rpm seems to be the Vtec engaugement point and also the exact RPM you run at typical highway speeds. By using a tire that has a diameter of about 1-2" larger I think it would in affect create taller gearing and keep the RPM below that gas guzzling Vtec engaugement point.

Just a theory, but I noticed a 3-5mpg loss this year doing the same trip... I went from a 205/40 tire to a 195/40 tire (17' rim). Granted I have other factors, have not really had the opportunity to test this theory out (mainly because it is expensive to get a whole other set of tires!)

Tire & Gas Milage Relationships (theories)
1) Larger dia = Better Highway mileage
2) Tires with higher treadwear ratings = less rolling resistance
3) Ligher rims/tires = Better City Mileage
4) Continous center tread > broken pattern treads for gas mileage
5) Get tires balanced at expensive shops = less weights needed and more presise balancing
6) Use 2-4lbs more tire pressure over reccomended when loaded with weight to counteract affect.
7) Summer Tires for Summer! Not all seasons!!