Hello, so my Son's 2009 Subaru came with Mobil SuprSyn in it, and didn't seem to have any issue for the 2,000 miles before I did major maintenance. I switched to WM 5W-30 synthetic during the timing belt service at 105,000. Oil level keeps coming up low after 2,000 miles despite adding more. Mechanic says it's probably burning oil at higher rpm. Without going to a thicker viscosity, which synthetic is known to have the best additve package to help retard this issue? Should I go with Mobil 1 and hope for the best?