More on modern oil in vintage engines

Question:

You answered the December question regarding oil correctly as it was put to you. However, there are other aspects regarding modern motor oil in vintage machinery. Many readers may not know that regulations require that current off-the-shelf motor oils have a lower quantity of phosphorous and zinc additives and new automobiles and trucks are designed to not require the same proportions our older machines do.

Perhaps many of your readers do not know they may not be getting the protection against wear that their cars require. In this regard the quoted Mobil 1-15W50 may no longer have 1200-ppm phosphorous and 1300-ppm zinc. To this I add that I have tried through various sources, including the manufacturers, to obtain the actual figures of these additives used. So far, I have not been able to obtain a definitive answer from any of them. There is one exception—a company that claims to be exclusively producing their oil with the additives in the required amount for antique and collectable cars.

My point is, would it be possible for you to disclose to your readers, how and where to obtain the amount of these additives used in our favorite brands? Furthermore, could you provide the amounts that would be safe (lower and upper limits) for our older engines in vintage and antique autos, trucks and boats?

As aside note, I have observed this with many of my older-model engines with hydraulic valve lifters: They do not like Mobil 1 or synthetic motor oil. That is, the lifters do not operate (pump-up) properly. This has caused noisy lifters and misfiring. In every case when this occurred, the symptoms stopped when oil was changed back to non-synthetic. Perhaps you could comment on this as well. I only found this out by trial and error.

Answer:

4 During the past year I believe we 2” have covered all of these questions except the one you ask about determining the amount of ZDDP in each brand of motor oil. The problem is, there are as many brands and types of motor oil as there are cars, and many of them dont tell us anything about the amount of ZDDP in them, most likely because there isn’t any.

Today’s oil is not intended for cars made 20 years ago or earlier. The market for such oil would be limited, and ZDDP damages catalytic converters, so it has been eliminated from most oils available for automotive use.

Zinc dialkyldithiophosphates or ZDDP for short, is a group of compounds developed in the 1940s to minimize scuffing and friction in engines that were being asked to produce greater performance than in the past. It is a sacrificial metal compound that provides a boundary layer of protection for cam lobes and flat tappets in the valve train. But it also helps protect crankshaft and rod bearings from scuffing and it acts as a corrosion inhibitor and antioxidant as well.

As we said, it was a standard ingredient in motor oil until cars were required to have catalytic converters, but because it damaged them, it was eliminated and automotive manufacturers went to roller tappets in their engines to cope with the loss. However, a few petroleum manufacturers are still producing motor oil with the necessary amount of ZDDP, and it is also sold as an additive to be used with modern oil.

The optimal zinc levels for older (pre1993) flat tappet engines are 1200-1400 ppm of anti-scuff molecules. How serious is the problem if your oil does not have ZDDP? Your engine will not abruptly self-destruct using modern lubricants, but generally, after years of restoring, upgrading and pampering our classics, we want the optimum.

And if you have altered your classic’s engine to produce more power, you most likely went to a hotter cam, which means that its nodes are broader, its ramps are steeper, and its valve springs are stronger so as to keep the lifters following the cam rather than floating and bouncing. All of that means dramatically greater pressure and wear unless you provide extra protection in the form of ZDDP. On most original engines, the wear would be slow and unnoticeable, but on hot rod engines it can be pretty quick and catastrophic.

As I said previously, Mobil 1 synthetic is suitable for older engines— especially those that are not stressed, as in a racing situation. I use Fischer Classic Car motor oil because it is specially formulated for vintage cars. It contains 1200-1400 ppm of zinc for maximum protection and it is local for me. You can find them at http://apfischer.com/

Another motor oil that will do the trick is Valvoline VR1 racing oil. It comes in several grades, and is designed to extend the lives of pushrod and flat tappet engines. It contains an ample amount of ZDDP, is race proven, and it is street legal for older cars without catalytic converters.

You also can use an additive such as ZDDPlus, which is available from ZPlus, https://zddplus.com/

As for the hydraulic lifters clattering on your older cars, I have never heard of synthetic oil causing slow lifter build-up. It is slicker than ordinary motor oil, and some say it flows so well that it doesn’t stay in one spot long enough, though I doubt that, but I don’t know of anyone who has had your problem. It makes me wonder if you are using synthetic of the right viscosity range, and whether the engines in your collection get run often enough. Are there any readers out there who can fill us in on this situation?