I have used Molbil1 and Q-Horsepower synthetic, both 5w-30 and no issue. You DO NOT want to be running thicker oil in the winter months with a turbo!

 

I have used Mobil 1 synthetic in everything since 1990 when I had bought a new Chevy Beretta GTZ with the Quad 4 and 5 spd. I had always been a Castrol GTX 3,000 mile oil guy until I noticed I was seeing a 5 PSI drop in hot oil pressure after about 1,800 miles on an oil change. I was talking about this with a couple GM 3800 V6 engineers and they told me all the good stuff about Mobil 1 synthetic. After switching to Mobil 1 synthetic, I no longer saw the 5 PSI drop in oil pressure and extended my oil changes up to 7,000 miles. G.B.

 

Royal Purple 5W30. Costs more, but I believe it to be a better oil.