zinc in motor oil

[FrankWest]

Was zinc introduced to motor oils in the 40's?
And is zinc needed for only new engines and rebuilds?
The modern engines limit zinc because it clogs the catalytic converters, right?
Does an original model a or B engine non- rebuilt still need zinc?
If it does, can a zinc supplement be added?

[MikeK]

No zinc (ZDDP) needed in an A or B. The stuff serves as an EP lube between Fe on Fe surfaces, such as flat tappets and a cam when the oil film strength has been exceeded. The valve trains in A's, B's, as well as most other engines never reaches that extreme. Only very high inertia and spring pressure setups will exceed the oil film strength necessitating a solid molecular backup to interfere with friction welding. You can just about squeeze an A/B valve spring flat by hand. Try that with a spring from a 60's era muscle car, the initial flat-tappet wear problem that prompted adding significant amounts of ZDDP to the oil additive package.

Some say 'Well, it can't hurt'. . . Yes, it can. Aside from killing cat converters the stuff makes the oil slightly lower in initial wet-film lubricity. That shows up in CAFE. You will get slightly lower gas mileage. Likely not noticeable, but if you are a manufacturer every 0.1 mpg matters.

Others may have varying views on the use of the stuff.

[FrankWest]

Originally Posted by MikeK

No zinc (ZDDP) needed in an A or B. The stuff serves as an EP lube between Fe on Fe surfaces, such as flat tappets and a cam when the oil film strength has been exceeded. The valve trains in A's, B's, as well as most other engines never reaches that extreme. Only very high inertia and spring pressure setups will exceed the oil film strength necessitating a solid molecular backup to interfere with friction welding. You can just about squeeze an A/B valve spring flat by hand. Try that with a spring from a 60's era muscle car, the initial flat-tappet wear problem that prompted adding significant amounts of ZDDP to the oil additive package.

Some say 'Well, it can't hurt'. . . Yes, it can. Aside from killing cat converters the stuff makes the oil slightly lower in initial wet-film lubricity. That shows up in CAFE. You will get slightly lower gas mileage. Likely not noticeable, but if you are a manufacturer every 0.1 mpg matters.

Others may have varying views on the use of the stuff.

Thanks....I needed that!!!!

[Skibb]

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Amen, we all needed that, thank you MikeK.