Flat Tappet Cams

Engine oils since 2006 and flat tappet cams……

Since 2006, a new designation for petroleum based motor oil was introduced which has virtually no “zinc di-alkyl diathiosphosphate” additive. Usually referred to as ZDDP. This additive has been in motor oils for more than 60 years and its anti-wear characteristics have been taken for granted by millions or motorists for generations. This is no longer the case.

The “new” oils have an API Service SM label on the oil bottle regardless of brand. The ZDDP additive was present in ever declining amounts in previous motor oils designated SL, SJ, SG, and older. Since all modern engines (since at least 1996) have either been equipped with steel camshafts and/or roller lifters, the additive is not required for these engines. Since the zinc additive damages catalytic converters when burned, even in small amounts, the ZDDP has been reduced by some oil companies by over 35% since 1997. Starting in 2006, most major oil companies have reduced the zinc and phosphate additive to zero.Older vehicle owners beware!

This means most 5W30, 10W30 (regardless of brand name) some SAE 30, and many 15W40 oils are lacking this crucial additive. For engines with “flat tappet” cams and lifters, the missing ZDDP additive means the lifters and camshaft lobes are slowly but steadily wearing away while you are driving even if you are changing your oil regularly.

For the next few years, some 15W-40 oils (usually labeled “long-life” or “for diesel use”) will still contain the zinc additive. Look at the label however! If it says “API service SL, SJ, or SG” it is theoretically safe to use in older engines, but if it says “API service SM” on the label, we don’t recommend using it in your pre-1996 engine unless you are running a roller cam or you have a Japanese or European OHC engine with a steel camshaft.

Currently (2012) most HD30 and some 20W-50 oils still have the SG designation and still contain the zinc additive. We carry Lucas and Joe Gibbs Driven in HD30 for vintage North American engines and Lucas in 20W-50 for older English cars. The diesel compatible 15W-40 oils with zinc is likely to disappear from the market within 2 years as the new “clean diesels” are now on the market. All major brands: Castrol, Pennzoil, Quaker State, Valvoline, and all the major oil companies have adopted the SM designation for motor oil in gasoline engines, so if you have an older vehicle without a roller lifter camshaft, read the labels on the oil you are purchasing carefully.

A few manufacturers such as BMW, Bombardier, and Castrol’s Syntec blend, have “long-life” 5W-30 and 10W-30 oils which have a molybdenum additive to provide an additional level of friction protection and these might be a reasonable substitute. Also adding a ZDDP supplement to currently available oils seems to be working for some of our customers. We carry Lucas Zinc-Plus and AC Delco’s E.O.S.Synthetics don’t care:

Because synthetic oils are refined in a different manner from a different base, they have different (better?) lubricating properties than conventional motor oils in a lot of areas. It should be noted that the viscosity of synthetic oils is usually much lighter/thinner than conventional petroleum based oil and these synthetics are generally factory installed and recommended only for engines since the late 1990s. Do not use them in older engines requiring 15W-40, HD30, SAE30, or 20W-50 oils. Viscosity of oil is similar to thickness, or restistance to flow. The lower the number, the “thinner” the oil appears. Most synthetic oils are very low viscosity : 0W-20, 0W-30, 5W-15, 5W-20, 5W30, 5W-40.

The high-performance, higher viscosity synthetics such as Royal Purple 10W-30 can theoretically be used in older engines as long as they don’t use a “rope” style rear main seal. (They leak even worse than normal with synthetic oil) While providing superior lubricating properties at both lower and higher temperatures than conventional oil, the synthetics do not contain ZDDP.

© Thompson Machine can be reprinted without permission.