Wow 15-50 is a bit much. The heaviest I would use on the VG30 would be 15-40, and I'm not convinced of the consequences of using that either. Remember, that oil has to be able to flow through the small passages in the turbo center housing at a respectable rate. You NA guys don't have to worry about that, but we do. 15-50, especially cold, I don't think has the right flow characteristics to keep the turbo properly oiled during warm up. I'm not sure how thick this stuff is at temperature either, but thicker is not always better. You could be masking an oil pump going out, in fact you may accelerate it's failure using the thicker oil. Also every seal and gasket in the engine will be stressed more by the higher oil pressure. Heck, I've seen 80 psi at idle from 15-40 when cold. Check what weight oil the car was supposed to use from the factory. For the VG30 I beleive it was either 10-30 or 10-40. Using the recommended weight oil and having a ticking problem should tell you something about your motors internal condition.
