Technically it had to/should run cooler because you have to circulate water through a convertor to vaporize the propane but what it dropped it I have no idea. You would have to run it on gas, document temps and then redo the same runs on propane. We always wondered but never took the time to research. We always ran either a 44gal or a 60gal tank, milage varied like everyone else, depended on the course. San Felipe was always the worst at roughly 2.5mpg, its pretty close gas, maybe a pinch under but the cool factor was the 110 octane and the price difference to race fuel. Took the propane off the 68' prerunner and haven't had the truck out since, so???