I should have known something would happen. The other day I switched from Craftsman 30wt oil to Pennzoil YB 10W-40. It seems to run great. After 45 minutes of mowing I look and notice a very thin white smoke almost invisible, coming out of the intake/filter. I shut it down, and as it slows down it starts puffing much whiter. Like puffs of white smoke. If I pull the starter cord slowly it puffs out the intake and exhaust, white smoke. If it was coming out of the exhaust I could understand, but... Out of the intake? Is this some side effect of the oil? Or is the engine messed up? Its a Briggs 675 Flathead with a season and a half of use.