I have a turbocharged 2000 Honda Civic. It's boosted at around 6 psi and driven daily. The recommended oil for the engine is 5w30. I've been using 5w30 Mobil 1 with good results. 5000 mile oil changes. Is the lighter oil better or worse on turbos?
Did you sample the 0w-20? I'd say RL 5w-30 or Mobil 1 R 0w-30. Checkout the new Mobil 1 R at Avlube.com. I'd use this if you race it. M1 15w-50 can't be ruled out but it's just something you'll have to monitor via UOA's to see whats going on.
Rabid, I'd use Red Line 5W-40, as I indeed am in my turbocharged car, a Porsche Cayenne. It has EXCELLENT high-temp/high-shear ratings, only 10% lower than that of M1/15W-50 and lots higher than any other M1 n-30 or -40 oil.
I would for sure go with 10w-30 or thicker, and choose an oil with as small of a viscosity spread as possible. Keep your oil change intervals shorter. You added an aftermarket turbo kit to an engine that was not originally designed to be turbocharged, so it probably has a smaller than required radiator and no oil cooler. Well, the radiator might not be an issue as I have a few friends with boosted B-series and they never overheat. But, non-the-less, your generating a ton more heat than stock, so I'd stay clear of 5w-20 and even 5w-30 for an aftermarket turbo application. By the way, what's your set-up?
Our 2003 Audi Bi-Turbo came from the factory with 0W-30 synthetic. I drive the crap out of it and the OCI monitor suggested I change it at 8,800 miles. I beleive in 0W oils. If you want more protection, go to a 0W40 like M1 or equivalent.