Royal purple is a lot of hype if you ask me. There's lots of other oils that work better for turbos.
What you want in an oil for a turbo is something that doesn't burn off in high temps and doesn't shear down to a lighter weight at high temps and high load. Most PDS (product data sheets) will have these specs for the oils listed as HTHS score (lower is better) and NOACK volatility test (lower is better). Synthetics are best for this and here are my favourites.
I like the Redline oils (best performance), Pennzoil Platinum and Ultra 5w-40 Euro (meets Euro turbo specs for peace of mind), Mobil 10w-40 High Mileage (most widely available), Shell Rotella 15w-40 (best value).
They're all rated for low scores in HTHS (high temperature, high shear) testing and have lots of good user results. Choose the weight based on your oil temps and have fun.