Reply to "Castrol Classic"

Zinc and phosphorus are the main ingredients in ZDDP. If your engine has a flat tappet cam then you pretty much have to use oil with ZDDP to prevent wear on the tappets and/or cam lobes. In the 1970's all oil had zinc for this reason. Then catalytic converters came along and zinc had to go because it fouls the cats. Detroit switched to roller cams at the same time zinc was left out of most engine oils. If your Fontana engine is flat tappet then zinc (ZDDP) would need to be added to the Castrol GTX 20/50. Valvoline VR1 has always retained its zinc content and that is what I have been running in my flat tappet engines. It is good to know that Valvoline VR1 has some competition now.

2/1/232:28 PM

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