thanks dub for the help. i didnt meen to ofend, i was teasin you. didnt see the link you posted untill after i replyed. im useing a not to smart phone, it doesnt always load everything on a page. i think i did the math right. the tyre size dif was 9.28%. so compansated i got 11.63 mpg. still seems like somethig is wrong.