Riehlife contributor Judy Tart sends this gas calculator from an AAA website. It allows you to calculate gas prices for a trip anywhere in the US, but only calculates between large cities. It does help compare between specific models of cars, which is very informative.
Judy calculated the gas cost for a round trip from San Francisco to LA driving either their Ford F-150 truck, or the Prius – Ford, $196, Prius, $62. “No contest, if you’re not hauling tons of luggage. For roughly $100 more, we could fly round-trip. I couldn’t calculate the cost for this trip using our Ford F-350 (camper), but it would have to be more than the smaller truck. I’m thinking a vacation trip where we might cover thousands of miles has got to be pretty expensive.”