T4 contains zero zinc as far as I know. It uses Ca Suphonate instead as an EP, corrosion-inhibiting, and overbasing component. It also contains a mega-load of ashless dispersants and antioxidants that aren't really needed in a gas engine except to suspend the sludge created by the shear breakdown of the viscosity modifiers, and is all in a mediocre base oil which is far too viscuous.
There are many reasons why lubricating oil for compression-ignition engines are formulated differently from that intended for spark-ignition engines, and why API, ILSAC, and SAE have specific (and vastly different) specifications for each. Best plan is to use the appropriate type for the application and supplement known deficiencies.
Ian still has 1000-1200 PPM ZDDP is NOT zinc free