Its very good. We've many m18/15/13 Swifts running on 5w30 liquimoly molygen, special tec without any hassle or wear and tear.
Even in scotching heat of summers you can use it.
If this was the case why cars run on 0-5w20/30 in middle east and uae and hot countries.. If heat is the case they should have 20w50 and 10w60 running there... Toyota is also introducing 0w16 are these manufacturers crazy???
You people are too much Trapped in to the jargon of heat, summers...