Hot Rod Oil.....any one heard of it?

Here’s an article out of Hemmings from 2012, in which they speak of continued reduction in zinc in the future as well as zinc requirements of older engines. There are many articles like it, from that period. My research dates from this period. 1200 ppm is the recommended minimum for new engines. Mobil One doesn’t meet that spec, except for racing oils. The PennGrade does, but states these oils are not recommended for use in cars with catalytic converters. I wonder how available this oil is?
About 6 or 7 years ago, before I was really aware of these issues and just used oil off the shelf I found several lifters in my stock engine had started to break up on the surface - that is they were pitting. In 40 years I’d never seen that. Since then I’ve used ZDDP additives, or Lucas Hot Rod oil and not had the condition repeat. Coincidence maybe, but I’m more cautious now.

The Mobil 1 15W-50 I use has 1,300 ppm. It’s not a racing oil.

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Ah, the evergreen subject of zinc raises its oily head again.

Notable that wear testing shows too much zinc to be deleterious, and with an XKs low spring pressure, likely not an issue at 1000ppm.


Hi John It is described by Mobil in their spec sheet as a oil for racing that can be used for high performance cars/flat tappet engines. Interestingly Mobil’s on line advertising that I’ve looked at does not mention the level of ZDDP, you have to look on their spec sheets, like the one David posted. How’s the consumer to know, out of a myriad of oil products that one oil meets the minimum requirements?

If there was ever an over thought topic, motor oils must be near the top of the list. I obviously do not have the data to back it up, but it seems to me the mass numbers of engine failures due to the new crap oils just has not materialized.


I’ve been using Royal Purple HPS which is a 20-50 that is some kind of synthetic blend with zinc and other stuff. It makes me feel good every year when I change the oil I feel the engine runs smoother.

Agreed: I have not read any definitive, non-anecdotal data dispelling the notion.

I ran Tweety on Walmart sale oil–with the highest API rating–and its 190,000+ cam loves and tappets looked just peachy.

As far as I can see, once a flat tappet cam is broken on… just keep the oil clean.

Ditto on my Rover.

Good point Terry. Maybe I should have said not advertised as a racing oil; but the specs say , “. . . racing and flat tappet applications”, where their racing oils don’t specify for flat tappets. And unlike two of the last four oils in the product specs guide it’s not labeled as a racing oil on the package (though racing is mentioned in the fine print no one reads on the back of the jug). Those two are also not recommended for street use.

Another key difference for me at least is I can find 15W-50 at my local Walmart for about $26 for a 5 quart jug, but they don’t stock Mobil 1 racing oil.

IMO, any oil you buy that has the correct SAE designation for your engine is good enough. I consider the XK engine to be slightly different only because it has flat tappets and there is a reasonable priced synthetic available that claims it’s designed for flat tappet engines.

Maybe the takeaway from all this is “Use what you are comfortable about pouring into your engine”.


Super-high levels of ZDDP do not necessarily equate to better wear protection.

  1. ZDDP binds to metal surfaces as a result of heat and pressure. But only to a certain extent. Large quantities of the compound doesn’t mean it will keep plating the wear surfaces with ever-thickening layers. Excess ZDDP just sits in the oil unused.

  2. If a test of one’s oil at the end of the oil change interval shows very low levels of ZDDP, then it would be prudent to use a product with a higher concentration. Otherwise, it’s a waste. Just like taking vitamins at 10,000 times the daily recommended dose. The human body only can use so much of the stuff at a time.

  3. There are other anti-wear additives other than ZDDP. ZDDP is one of the cheapest anti-wear additives available, so removing it doesn’t save money. The stuff still has to pass SAE, ACEA, and JASO standards. Tribologists aren’t snake oil salesmen. For the racers, ZDDP actually can increase friction (a small amount) but reduces wear (as it sacrifices itself instead of the sliding surfaces.)

Higher level ZDDP oils or supplements are a good idea for break-in of new engines, since those have no prior protective layer of anti-wear additives, so having some extra can help. (or changing the oil around 500-1000 miles, just in case the anti-wear additives were depleted by the needs of the new engine.)



Here is the 2018 API specification sheet for API SN oil, which has no zinc limit showing, but does show phosphorus limits of 0.08 (and implies a zinc limit via ZDDP chemical structure) for oils with weights under 30 viscosity and no regulation for higher viscosity grades. The API Service Symbol donuts in this document have the smooth outer ring, in contrast to the starburst API Certification Mark signifying latest ILSAC minimum performance standards are met.

In terms of zinc in motor oils today, maybe it is good to read at Mobile Oil about the current ZDDP levels used in modern engines. See

Does anyone know of specific engine motor oils that do not contain zddp and for what application are they recommended?

API SN Specifications 17thed1509addendum7rev021218.pdf (230.6 KB)

not all zddp is created equal. read joe gibbs driven oil website re zddp.

A useful source for ZDDP as used in car engines is the work of Professor Hugh Spikes of Imperial College, London. See . He has studied ZDDP for decades and co-authored papers with researchers at Royal Dutch Shell, Unilever, Castrol, Ford Motor Co., Pennzoil, Ashland, and many others. His 2004 review paper “The History and Mechanisms of ZDDP” in Tribology Letters v.17, issue 3, pages 469-489 remains widely cited very year and discusses why ZDDP is so widely used, even in the catalytic era. A useful example, Figure 5 in that paper shows how higher pressure valve operations, such as found in racing engine applications, need thicker ZDDP film thicknesses to avoid wear scars. His 262 publications have ZDDP in the title from as early as 1983 and up to December 2019.



Science, not anecdotes… off to read.

Good stuff, thanks Roger

Just as important for run-in/break-in is NOT to use synthetic oils for a while, as they prevent proper seating of the rings…

Damn but is it verified by a 93% consortium?

This is what I have started to use , it’s a local firm to me , they deliver free , and its at a very good price !

But they don’t deliver to the US.

I’ve been wondering about that. Don’t many new cars, all with freshly built engines come from the factory with synthetic oil?