Aoa. I would like to share my experience regarding engine oil. I previously used Toyota genuine Patron 10w30, and after only 2500k drive, tail Pipe became black inside. Last week I visited murree from Islamabad, and on every steep ascend, occasional smoke from tail Pipe was visible. I recently changed oil from Toyota to shell heilix hx7 5w 30, after 200km drive, now tail Pipe is quite colourless, and drive is smoother.
Moral: Don't use Toyota recommended engine oil in your belta. (comments pls)