Steve L

Why do the aftermarket cam companies such as Crane and Competition Cam and several oil companies also believe that decreases in the ZDDP level are causing flat tappet cam failures? Quotes from companies availabe per:

http://www.highperformancepontiac.com/tech/hppp_0802_pontiac_performance_engine_oil/index.html

Why are there a growing number of cam/lifter failures among professionally rebuilt vintage street/race engines using tried and true break-in procedures? If it’s not due to oil issues, could there have been a metallurgy change in terms of where the cam billets or lifters are now coming from?

Before debunking this myth, we need to look at the history of ZDP usage. For over 60 years, ZDP has been used as an additive in engine oils to provide wear protection and oxidation stability.

ZDP was first added to engine oil to control copper/lead bearing corrosion. Oils with a phosphorus level in the 0.03% range passed a corrosion test introduced in 1942.

In the mid-1950s, when the use of high-lift camshafts increased the potential for scuffing and wear, the phosphorus level contributed by ZDP was increased to the 0.08% range.

In addition, the industry developed a battery of oil tests (called sequences), two of which were valve-train scuffing and wear tests.

A higher level of ZDP was good for flat-tappet valve-train scuffing and wear, but it turned out that more was not better. Although break-in scuffing was reduced by using more phosphorus, longer-term wear increased when phosphorus rose above 0.14%. And, at about 0.20% phosphorus, the ZDP started attacking the grain boundaries in the iron, resulting in camshaft spalling.

By the 1970s, increased antioxidancy was needed to protect the oil in high-load engines, which otherwise could thicken to a point where the engine could no longer pump it. Because ZDP was an inexpensive and effective antioxidant, it was used to place the phosphorus level in the 0.10% range.

However, phosphorus is a poison for exhaust catalysts. So, ZDP levels have been reduced over the last 10-15 years. It’s now down to a maximum of 0.08% for Starburst oils. This was supported by the introduction of modern ashless antioxidants that contain no phosphorus.

Enough history. Let’s get back to the myth that Starburst oils are no good for older engines. The argument put forth is that while these oils work perfectly well in modern, gasoline engines equipped with roller camshafts, they will cause catastrophic wear in older engines equipped with flat-tappet camshafts.

The facts say otherwise.

Backward compatability was of great importance when the Starburst oil standards were developed by a group of experts from the OEMs, oil companies, and oil additive companies. In addition, multiple oil and additive companies ran no-harm tests on older engines with the new oils; and no problems were uncovered.

The new Starburst specification contains two valve-train wear tests. All Starburst oil formulations must pass these two tests.

- Sequence IVA tests for camshaft scuffing and wear using a single overhead camshaft engine with slider finger (not roller) followers.

- Sequence IIIG evaluates cam and lifter wear using a V6 engine with a flat-tappet system, similar to those used in the 1980s.

Those who hold onto the myth are ignoring the fact that the new Starburst oils contain about the same percentage of ZDP as the oils that solved the camshaft scuffing and wear issues back in the 1950s. (True, they do contain less ZDP than the oils that solved the oil thickening issues in the 1960s, but that’s because they now contain high levels of ashless antioxidants not commercially available in the 1960s.)

Despite the pains taken in developing special flat-tappet camshaft wear tests that these new oils must pass and the fact that the ZDP level of these new oils is comparable to the level found necessary to protect flat-tappet camshafts in the past, there will still be those who want to believe the myth that new oils will wear out older engines.

Like other myths before it, history teaches us that it will probably take 60 or 70 years for this one to die also.

Special thanks to GM’s Techlink
- Thanks to Bob Olree – GM Powertrain Fuels and Lubricants Group

The options are very simple. Any of the diesel rated oils such as Rotella (shell), Delo (Chevron) or Delvac (Mobil) are excellent oils that meet all API gasoline and diesel specifications, have much more ZDP in them than the ILSAC rated oils and do NOT have friction modifiers. 15W40 Rotella/Delvac/Delo is readily available in most any store and is an excellent choice for most any engine.

Cams/lifters are not the only thing to worry about. Distributor drive gears are problematic when ZDP is reduced as well as rocker arm pivots, spur gear oil pumps and older style timing chains. ANY engine older than the early 90’s is probably better off using the Rotella or Delo or Delvac.

Newer engines have been redesigned with roller lifters and roller rockers as well as roller timing chains, gerotor oil pumps and the distributor drive gears are no longer required…so they are perfectly happy with the ILSAC oils rated “for gasoline engines.”