it'll definately improve the mileage for sure. but with lpg i can get bottled gas for forklifts at less than one quarter the price of petrol here in the uk. so 'pound for pound' (or dollar for dollar) a 10 mpg big block will do the equivalent of 40+ mpg. plus i won't use petrol at all so i can use more timing advance as lpg is about 110 octane so i won't lose any power either.
