so i just bought i rig and drove it going back home for about 12 hours. the owner told me he used to get about 16 or 17 mpg and i din't really belived him but i drove it home nice and easy like i like to cruiser and i got raning from 17-19 on my fill ups 17 being driving up and down hills comming from california 19 on straights.. anybody heard of this before? i thought my odometer was bro or something but checking it with mile markers is on... any thoughts? has the stock 6l with a crazy california emision hook up andrequilt carb and block.. anybody any ideas i never hear of these many MPG on this kind of rig