I ran used Honda GN4 out of a 400EX in an old Murray riding mower with an oil burning and leaking Briggs and Stratton. I would change the oil on the atv after any time I ran it at the sand drags. I assumed that was doing my clutch and engine a favor(probably just over maintaining in reality).I was considering running used oil from our other vehicles in my pickup when the head gasket was leaking a quart every 75 miles.
Eventually, I opted to get the head milled down past the coroded oil port.
Eventually the atv started burning oil so I switched it to a cheaper oil. Wasn’t long before I moved and sold it. After the move I pulled the engine on the mower and fixed the leak so it just burned but didn’t leak oil.