Dr Lee, Taking the case of adding zdp(STP 4 cyl oil) to the oil at oil change time does this also apply to the synthetic oils also?
In addition to my project truck I also have a 04 VW Golf TDI that serves me quite well on my 65 mile RT for work, Would that apply to it as well cause the 04 requires a fully synthetic 5w40 found locally in only Castrol and Mobil 1.
Changed at 5k intervals as per dealer instructions.
As usual your thoughts are appreciated.....Merle