I tuned a couple of those up this year. I warmed the engines, drained the oil and put in Super Tech SAE 30wt. Better safe than sorry I told the customers. I recommend they see me every two years for an oil change, blade sharpening, complete fuel system cleaning and a new plug. I tell them that I will trust the new "no change" oil in about 5 or 6 years if I don't have a steady stream of worn out engines coming across my bench. Kind of like the latest prescription medicines. If they're not having their socks sued off them after 5 or 6 years, I'll be happy to try them too.