15 gallons seems like a lot, but a lot of that time seems to be on synthetic to get there. Some of my buddies are now just running 10 gallons of lawn boy or equiv to break these 3ws in, instead of running 5 gallons then switch, who knows for sure, but it seems 15-20 gallons through the motor gets the motor running sweet (not like they dont run fine out of the box).

Always, I would do some research on the 58, its a bad mother, but have seen videos of the 2.3 on the old style zdz 80 and its bad ass too.