I don't think anyone here at
I don't think anyone here at this forum really understands what the heck is going on in their engines: IT HAS NOTHING TO DO WITH THE GASOLINE !!! It is oil vapors coming from the crankshaft via the Positive Crankcase Ventilation system that is causing all of these problems. You have to STOP the oil vapors from flowing from the crankcase to the intake valves, it is as simple as that. Find out what hoses go from the crankcase to the intake duct-work / tract, removed them from the air intake, and plug the holes in the air intake that are left behind. If you don't plug the holes in the intake then you get a massive vacuum leak and your car won't run right. The hoses that come off from the crankcase: just leave them open so the vapors from the crankcase are vented into the atmosphere. if too much oil vapor is making an oily mess of your engine bay then add a longer length of hose so that the oil vapor is exhausted down near the bottom of your engine, so it flows onto the ground under the car. Just remember to re-connect everything back to the normal way it was for your annual emissions test, that's all. If you do this then the oil vapors from the crankcase won't deposit themselves onto the hot intake valves, its as simple as that.
Using gasoline with additives won't stop oil from depositing itself onto valves unless the car has PORT INJECTION on it. If the car has PORT INJECTION then the additives in the fuel will help clean the intake valves because the spray of fuel is blasted directly ONTO THE VALVES themselves, cleaning them with the spray. But in a pure direct injection car there is none of this spray of gasoline onto the valves so additives in the gasoline or the quality of the gasoline has ZERO EFFECT.