Frequently Asked Questions


  • Why do I need to be concerned about the current engine oils if I have a classic car or hot rod?

US government regulations (from the EPA), in an effort to make catalytic convertors in modern cars last longer, have forced the engine oil companies to seriously reduce the level of anti-wear protection additive in the current API SM/ILSAC GF-4 passenger car engine oils.

  • What could happen to my classic car or hot rod if I continue to use oil without enough anti wear protection?

The anti-wear chemistry, known as ZDDP, is in all engine oils to protect the camshaft lobes and lifters (known as flat tappet cams) from wear. For classic cars, ZDDP must be in the oil in a higher concentration than it is in current oils. Without ZDDP protection the cam and lifters will experience premature wear and eventual failure.

  • I am using a synthetic, I’m protected, right ?

Today’s synthetic oils are marvels of engine oil engineering. However, all API SM/ILSAC GF-4 engine oils, regardless of whether they are synthetic or conventional, must conform to the exact same standard on ZDDP concentration. Therefore, current SM/GF-4 synthetics will not have enough ZDDP anti-wear protection for your classic car’s flat tappet cam.

  • How soon after using current SM/GF-4 oil in my classic car could I have trouble occur?

The higher the valve spring pressure and the higher the engine rpm’s, the higher the ZDDP concentration must be for proper protection of a flat tappet cam and lifters. If the thin surface layer of hardened metal on the cam lobes and lifter faces has been compromised, rapid wear of these parts follows. Big block engines (high valve spring pressures) have been reported to have had failures in as little as several hundred miles.

  • I’ve heard about this problem and I’ve heard that I can use diesel oil or racing oil to protect my flat tappet cam engine. Am I doing the right thing?

Diesel oils and racing oils have stepped in as a band-aid attempt to help classic car owners due to the lack of passenger car engine oils with the correct level of ZDDP anti-wear protection for their classic flat tappet cam engines. However, neither diesel oil nor racing oil is properly formulated for continued use in a street driven gasoline engine. Continued use of diesel oil or racing oil could result in other problems for your classic car engine. Please refer to the attached discussion “Why NOT diesel or racing oils?”

  • What is Cam-Shield™? 

Cam-shield™ is a premium concentrated ZDDP anti-wear engine oil additive that you add to your favorite passenger car engine oil. Cam-shield™ restores ZDDP anti-wear protection in your favorite engine oil to the correct level for protection of your classic car cam and lifters.

  • Why do I need Cam-shield™?

Cam-shield™ is the only ZDDP product available that is concentrated enough to be used for either new cam break-in or running operation. Cam-shield™ was designed by a Senior Race Oil and Field Test Engineer from a major oil company. Cam-shield™ is designed to be highly concentrated so that you only need a very small amount to treat your oil – it is very important not to dilute your engine oil with “filler” used to make larger bottles of oil treatments as this will alter the performance integrity of your favorite engine oil. Cam-shield™ is designed with a proprietary blend of primary and secondary ZDDP for full temperature range coverage of your engine. Cam-shield™ is supplied in a unique bottle that lets the user treat their exact oil volume at oil change time or for top-ups.

  • How do I know if I have a flat tappet cam and that this problem affects me?

Virtually every American-made vehicle, and many foreign-built vehicles manufactured before 1975, has a flat tappet cam engine. The tappets are also known as lifters and can be either hydraulic or mechanical (solid). Flat tappet cam engines are also known as overhead valve engines. Modern engines with overhead cams or roller cams are not affected.

  • Why haven’t I heard about this problem before now?

When cam failures started increasing dramatically right after the introduction of the current API SM/ILSAC GF-4 category, it became clear that the level of anti-wear had been lowered to a point of intolerability for the classic car flat tappet cam engines. There has been a lag in this information reaching the actual owners of these vehicles.

  • Where I can I learn more about the effects of insufficient ZDDP in classic car engines?

Many articles and technical bulletins on this issue are now available to read.
Note that the quality of information is still improving as people continue to learn the fine points of engine oils as they apply to anti-wear performance in flat tappet cam engines. In particular, the continued use of racing oil or diesel oil in a street driven classic car or hot rod with a flat tappet cam engine is not recommended.

  • Hot Rod Magazine, “When Good Cams Go Bad”, June 2006
  • “Oil Is Killing Our Cars, Parts I (2007) & II (2008)”, Keith Ansell, Foreign Parts Positively
  • Engine Professional Magazine, AERA, “Flat Tappet Camshafts & Oils”, January 2008
  • Engine Professional Magazine, AERA, “The Lost Lobe Chronicles”, January 2008
  • Comp Cams Technical Bulletin #255, “Flat Tappet Camshaft Failures”, March 2008
  • Crane Cams Installation Instructions #548E, “Flat Tappet Camshaft Break-in Procedure”, February 2008