Well first time posting/registration. I have lurked on this forum for a long enough. I am in need of some expertise. I currently have a 2010 chevy cobalt SS turbo that is fairly modified. OEM oil is M1 5w30 and stock boost was 16 psi. The car as 45k km on it, and only summer driven. After 5k km, i switched to AMS 5w30 and have been changing it about every 5-7k. The car has been tuned for 26 psi for the past 30k km or so. This car suffers from direct injection carbon build up on the valves (bmw owners will know this). I will be walnut blasting the valves, installing an actual working oil catch can as well to help prevent this build. As well, i am about to install a meth kit to spray just before the intake. What i am asking is this. Most people recommend a low ash oil to help prevent against the build up, but i also want something to help with the addition of the meth to the mix. Meth will be spraying at a 50/50 mix after 10psi. Do i just keep with the 5w30, or go with a 5w40? I was thinking Mobil 1 ESP Formula 5W-30 or AMS European Low-Ash formula. Any help would be greatly appreciated.