A buddy of ours got a 2002 3/4 ton chevy pick up and automatically changed the standard tires to bf goodrich trail 285 16's and lost gas mileage. He took it to the dealer and they switched out his speedometer and said thats all they could do. Is there anything else out there he could do? Anything else out there he could add on or buy to correct this. I am sure he will not go back to smaller tires because he does alot of off-road traveling and he likes those big tires. But if there was nothing else he could do maybe he would give me a deal on them and go small. HELP PLEASE!!! '85 k-5 gmc jimmy 4x4 sierra classic. '84 k-5 gmc jimmy sierra. '70 cuda 440 6 pack executive edition shaker hood, steering column shift.