I have a 94 S10 ,4.3 V-6 5 spd as a regular driver.I have owned this truck since 1996.Has 100k miles .When driven on the freeway at reasonable speeds, the truck gets 27 mpg, day in day out. Lately the gas mileage has dropped to 25 mpg.I checked the throttle body injection fuel pressure,no codes stored in the computer and a vacuum guage says everything is fine with the engine and no clogged converter.The engine runs just the same as always, same power etc.The mileage drop has been sudden, not a gradual thing.I Buy fuel at the same Sunoco station down the road. Maybe their fuel formula has changed?
