I've read and heard of a lot of issues with Toyota's VVT-i and Hyundai's CVVT which can rattle loudly on start up from stuck or broken gears in the VVT actuator. Now I've searched on here trying to find this out, but have come up empty so far. I had thought that viscosity must be the answer to better VVT protection, but those two manufacturers recommend different weights (0W-20 for Toyota, 5W-20/30 and 10W-30 for Hyundai). So now I'm looking at different additive packages and how that might help. When it comes to taking care of the VVT, would you be more concerned with the lower viscosity oil or do you look for certain additives in the viscosity of your choosing? Sorry if this has been covered before, I couldn't find it if it has.