Lots of info to digest. The car only calls for 5-30, no other weights. 10-30 during warm months imo will cause no issues. 5-20 imo will because it's to thin. What if I were to use the 5-20 and throw in a bottle of liqui moly motor oil save that I have? Would that thicken the lighter oil? The cars an oil burner but runs very strong so I don't wanna put the final nail in the coffin.