Liqui Moly has a 507 oil for TDI that has low ash content for Diesel engines for VW cars. Yet for gasoline engines, they recommend that i use 505 oil in VW engine. And the higher ash count vs 507 oil, more ash acts as lubricant in gasoline engine in VW. Is this true? Does higher ash content act as lubricant? Ive tried googling but i got bunch of pdf documents that arent related to my question. If ash is not a lubricant, should i use 507 oil in a VW gasoline engine for the pure benefit of low ash? Thanks in advance.