Hey everyone I'm chasing down a misfire on my wifes 2011 Prius. The issue is oil is getting into the combustion chamber and is coating the plug causing no spark/misfire. P0303 is the code. The plug looks like someone dipped the electrode/threads in a vat of oil. It's coming from underneath the plug so not an easy valve cover gasket fix
. That means it's one of two things. The valves or the rings. I tried doing a piston soak on cylinder 3 only and still no go. I pulled the denso plug on cylinder 3, poured around 4 oz of MMO, let it sit overnight, came outside the next morning, looked down the spark plug tube, and the piston was bone dry. That means the mmo leaked past the piston. I cranked up the engine (with the plug out on cylinder 3) with a rag above the hole to see if any mmo would splash out and nothing. Is it normal for MMO to leak past the piston in 8 hours or so?