You shouldn't run any oil much thicker than what the engine was designed to use. Running thick oil to stop smoking or ticks isn't very wise. Most cases you're just masking the problems that you should be fixing your attention on. Too thick and you could risk oil starving some parts of the engine. Most factory boosted cars recommend 5-30 or 10-30 depending on your climate. I'd stick with 10-30 i've always ran that in my engine.