the methol hydrate thing works but i have'nt used it. my old boss used to do that he says it works. methol hydrate will burn pretty clean. he would go in with 1/8 of a tank of fuel mixed with a couple of liters of fuel. but as soon as he was done the test he would fill the tank up. i dunno about this technique but it should work. years ago we used to run a junky dodge d-50 little pickup on methol hydrate and that thing started to back fire really loud after a while (with a straight pipe none the less).
