At that rate of consumption the thicker the better. Unless he's in an area where he's routinely trying to start the engine in temperatures below 30 degrees, I'd recommend straight 50 weight racing oil. He's going to encounter spark plug fouling pretty routinely due to the oil getting past the piston rings, and if he lives in Commiefornia, the CARB will probably be after him for putting out too much blue smoke from the tailpipe!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!