i have a 97 4runner, and i have a somewhat similar issue with the gas gauge. It reads "normally" till it gets low, and then the light comes one, when about 14.5 of the 18.5 gallons is comsumed. I have just grown used to it.. Its actally really nice for road trips. Light comes on, i still have about 4 gallons left to go on.. more than once that has been a good thing.