I'm just referring to what i've experienced ... briggs intek 19hp. "Hey, i put i BRAND new engine on my mower, it's blowing quite a bit of smoke at start up" "what oil are you using?"
"*starts with M ends with 1 10W30",,, "change it out to a good quality 10W-30 conventional oil and a new filter and call me back" ...........few days later, "hey i changed the oil to conventional, it blew smoke on the first start up, virtually none since... hasn't blown smoke near as much since i switched. just a slight puff". (valvoline 1030 was used if i remember right).... "Okay, great, glad i could help"
i believe he got to around 8 hours of mowing time and it completely quit burping out a little puff of smoke with the conventional.... he switched to Synthetic at 20 or 25 hours.... and it did fine.