This was taken from Royal Purples website:
Quote:
Do your motor oils contain zinc and phosphorous?
Yes. All Royal Purple engine oils contain the zinc/phosphorous compound zinc dialkyl dithiophosphate (ZDDP) and are suitable for both roller and flat tappet valve trains.
Can your oil be used with flat tappet cams?
Yes. For stock or mildly modified flat tappet valve trains (<.525” lift), we recommend our SAE 10W40, 15W40 or 20W50 engine oils. In applications with flat tappet valve trains using high-lift cams and/or high RPM applications, we strongly recommend upgrading to our XPR line of engine oils as these have an even greater concentration of ZDDP providing excellent protection with the higher spring pressures. For a viscosity recommendation, contact our Tech Dept. at 888-382-6300.
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1981 Porsche 928 "Euro" Auto Gunsmoke Metallic Flat - Black Interior
1983 Porsche 928S "US" Auto Light Bronze (Copper) Metallic - Brown Interior **SOLD**
