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Engine oil has always been an interesting topic as well as constantly changing to accommodate modern engine technology.
Hot Rod Magazine covered the subject very well in an article published June 2006 titled "When Good Cams Go Bad". Comp Cams also has an excellent Tech Bulletin titled Flat Tappet cam shafts and can be reviewed at www.compcams.com.
All modern high tech engines with push rods use roller tappets and overhead-cam engines use either roller or sliding tappets.
"In an ongoing attempt to keep emissions as low as possible, manufactures have been putting tighter and tighter limits on how much phosphorous and zinc can be in the motor oil" Mark Ferner, Quaker State.
Older engines including all early Thunderbirds have flat tappets. "Engines with flat-tappet cams have extremely high pressure loading at the contact point between the lifter crown and cam lobe" (Hot Rod Magazine). In the past conventional motor oil included a generous supply of anti-wear additives, a combination of zinc and phosphorous (ZDDP). Ferner adds, "The zinc reacts with the cam lobe’s iron surface and creates a sacrificial coating strong enough to keep parts separated to reduce the wear." ZDDP is not required in modern engines and has been reduced in most modern oils because as it flows through the exhaust system on worn engines it has been blamed on degrading oxygen sensors and catalytic converters. "It will only get worst because projected future oil spec revisions will likely reduce ZDDP content even more" Hot Rod Magazine.
OK, What can we do? It is not all gloom and doom for our Thunderbirds. The Hot Rod Magazine article as well as the COMP CAMS Tech Bulletin emphasizes the importance of oil with ZDDP during the camshaft break-in period. Most engine shops can provide the proper oil for camshaft break-in and NAPA and other stores also have camshaft break-in oil.
All engine oil containers have API Service ratings on the exterior of the container. Modern heavy-duty diesel engine oils have lots of ZDDP additives and will be marked "CI-4 or CI-4 Plus" Diesel oils also have additives that pass all gasoline engine performance tests. Some racing oils also have adequate amount of ZDDP. Check the API ratings on the container.
Hot Rod Magazine list the following API designations or brands as having ZDDP content: SM, SJ, SL, SM, Cosworth Racing, Shell Rotella T, Pennzoil 20W-50W Racing and Quaker State Q Racing.
I recommend reviewing (Google) the comments made on line regarding engine oil, the Hot Rod Magazine article and the COMP CAM Service Bulletin.Click Here for more on Engine Oil and ZDDP