When I used to sell used cars a few years back, whenever we ran into a car with a very quiet engine, we assumed the owner used Mobil 1. Many of them did, especially truck owners. I haven't ever noticed M1 making an engine noisier, but I guess it's possible. Chevy has no problem recommending M1 5W-30 for some very hi horsepower V8s, so it can't be too bad.