I have done a bit of research regarding my cars engine oil. My handbook and information on this forum state to use 0w-20 grade. Now other places like Halfords, EuroCarParts and even Opie Oils recommend 5w-30! I know that 0w-20 come as Synthetic oils, but there must be a reason why Toyota prefer that grade. Other grades should only be used as substitute as top up only. At oil change time, the correct/preferred grade is 0w-20, as stated in the handbook. I think the term used is "Optifit