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What is ZDDP

In a 1977 Triumph Spitfire, using Mobil 1, why would I need a racing oil with ZDDP?

It Never Hurts To Add A Little Zippidy-Do-Da To Your Sports Car!
I believe ZDDP was originally introduced for use in Zundapp motorcycles, or maybe I just made that up.

On a more serious note, they (ZDDP oil additive folks) have a website.

Am I falling for a commercial?

You don’t even need Mobil 1, much less a racing oil. Use any (inexpensive) brand of oil with the viscosity specified by your owner’s manual. The poorest oil you can buy today exceeds the best oil available in 1977. Also follow the manual’s recommendation for oil changes.

If your Spitfire is anything like my TR6. It leaks ferociously with most multi-weight oils. I’ve been using straight 50 weight Valvoline VR1 oil. It doesn’t leak as much. A nice side effect of this leaking is that the undercarriage stays rust free!

Not To Mention The Benefit Of A Perpetual Oil Change!

A little ZDDP is good for your flat face valve lifters to minimize wear unless your engine has roller lifters. Current engines have roller lifters which can get by with very little ZDDP which tends to poison cat converters. Use a couple of quarts of diesel oil plus your regular oil to get enough ZDDP for your older engine.

ZDDP is an ingredient in oil that reduces wear in a hydraulic lifter setup. It protects the camshaft.

Most modern engines have roller rockers, which reduces the need for ZDDP. ZDDP is bad for your catalytic convertor, so modern oils have less ZDDP than a traditional engine would need. ZDDP is also being phased out of diesel oils. I am aware of a company that sells a ZDDP additive, and I’ve also heard about a racing oil with ZDDP but I think that is only 20W50.

In my old car, I use an off-the-shelf motor oil with the ZDDP additive.

It’s petroleum distillates, paraffinic hydrocarbons (dewaxed), and zinc dialkyl dithiophosphate. The paraffins and the phosphate reduce wear; the petroleum products are a carrier.

The real problem comes if you get your engine rebuilt and the camshaft reground. Once reground, the cam is likely to wear down very quickly and your mechanic will blame it on oil that does not have enough ZDDP and MoS2 in it.

The real problem is in the manufacturing process used to make the camshaft in the first place. A 77 may not have this problem but older vehicles did. Prior to sometime in the 70’s or 80’s, the common practice was to use a mild grade of steel, machine it to shape and the case harden it. This was done because they didn’t have the super hard cutting tools that we have today.

Today, harder steel is used in the first place because we have better cutting tools and it saves on labor by eliminating a step.

If the old cam is reground and not re-hardened, it will wear down quickly. Many modern machinist don’t seem to be aware of this, or they forgot it since school because they haven’t had to use it.

If you are still concerned, you can use straight 30 Penszoil, it still has the Z7, or you can use any good diesel oil, there is even a synthetic 5w40 diesel oil.

Here is the original article that started the ZDDP hysteria from Hot Rod explaining some of the reasons for Cam failures in Flat Tappet engines.