Technical Article

Oil Changes

(as appeared in the Nov, 2008 TSR)

By John Wright

Mike Hughes draws our attention to the following article: “More than an Oil Change”. by Jonathan A. Stein, reprinted courtesy of HagertyPlus, LLC, copyright 2008, at

Formula modifications could mean it’s time to reexamine the oil you use in your collector car. Most car enthusiasts can probably rattle off the automotive products that they’ve relied on for years. But when it comes to oil, recent composition changes driven by environmental concerns could mean your preferred brand of oil may not work so well in your collector car today.

Many older vehicles use overhead valve engines with flat tappets that contact the camshaft lobe on one end and the rocker arm assembly on the other. The rocker arm assembly is relatively heavy and generally has a big valve with a heavy spring, resulting in a lot of pressure on the tappet and camshaft.

Years ago, oil companies and automakers discovered that zinc dialkyldithiophosphate (ZDDP) was effective in reducing cam and lifter wear, as the compound interacts with the iron of the cam lobe and creates a sacrificial barrier. As of 1988, the ZDDP concentration in oils certified by the American Petroleum Institute (API) standardized at up to 1200 PPM (parts per million) phosphorous. However, phosphorous levels were brought down to the 800 PPM level by 2004 because high phosphorus concentrations shorten catalytic converter life in modern cars, and modern roller cam engines don’t require ZDDP’s protection.

Soon, rebuilders of flat-tappet engines – particularly those from the 1950s to the 1970s – were noting increased cam failure on newly assembled engines. Many engine builders have tied the failures to the reformulated oils, although API spokesman Dennis Bachelder asserts that API-ranked oils are compatible with older vehicles and the ZDDP levels in current SM-rated oils are sufficient to protect flat-tappet engines.

PPM SM-rated oils, try these options:

  • Oils rated for both diesel and gasoline engines (up to 1000 PPM) are available from Shell and Chevron.
  • Valvoline’s VR1 Racing Motor Oil ( has up to 1300 PPM of ZDDP.
  • Castrol’s SYNTEC 20W/50 full synthetic product ( has 1200 PPM of ZDDP (check that the rear label says Recommended for Classic Cars), and Red Line Motor Oils ( – also synthetic – have about 1300 PPM zinc and 1200 PPM phosphorous, although synthetics aren’t suited for the break-in period.
  • BRAD PENN Penn Grade 1 Racing Oil ( is a mineral-oil alternative with nearly 1500 PPM of ZDDP.
  • Classic Car Motor Oil ( from the Indiana Region of the Classic Car Club of America manufactured and bottled by D-A Lubricant Company, Inc. ( contains 1500-1600 PPM.
  • Use a ZDDP additive such as ZDDPLUS ( or Cam-Shield ( with every oil change.
  • Additional protection, essential during the start-up phase for any fresh engine, can be provided by generous use of an assembly lube with a large dose of ZDDP like GM E.O.S. Assembly Lube (PN 1052367).

With these options, there’s no need to worry about your camshaft. But it’s always a good idea to line up supplies along your route before you take to the road.