Going to do an oil change in a Buick Grand National. Going to use Catrol 0W-30 GC. I also have on hand a few bottles of Zddplus. Would it hurt to add a bottle? Any negative effects from adding this to the GC?
The GN's used flat tappet cams IIRC. I used Rotella in mine and it used to be popular with the GN crowd but it doesn't have the good stuff in it it used to have. ZDDP will help. The Valvoline VR1 would be my oil of choice for the GN.