Info from Cam-shield(TM)
Hello,
Very interesting thread. If I may, I'd like to offer some insights on the issue of current engine oils and flat tappet cams.
Yes, the current API SM/ILSAC GF-4 engine oils are subject to industry limits on Sulfur and Phosphorus. This is to provide additional life to the catalyst. Sulfur and Phosphorus are know to degrade the catalyst effectiveness. The allowable levels of Sulfur and Phosphorus in engine oils have been declining for the past few API gasoline performance categories, the latest, SM, seeing the largest decrease. In API SM/ILSAC GF-4, Phosphorus is limited to 0.08 weght percent maximum (800 parts per million (ppm)). Sulfur is 0.5 weight percent. The API SM/ILSAC GF-4 grades are referred to as the fuel economy grades and are 0W-20, 5W-20, 0W-30, 5W-30, and qualified 10W-30's. The API SM grades that are not ILSAC GF-4 fuel economy grades are 5W-40, 10W-40, 15W-40, 5W-50, 10W-50, 15W-50, 20W-50. Many of these products are manufactured with the same additive packages as the fuel economy grades and thus may also be 0.08 weight % Phosphorus.
As it turns out, the anti-wear chemistry in engine oils, ZDDP (Zinc dialkyldithiophosphate) is a Phosphorus, Sulfur, Zinc and hydrocarbon branch molecule. In order to lower Phos to 0.08wt %, the ZDDP level needed to be reduced. The current fleet of modern vehicles has different engine designs (roller lifters, lighter valve spring pressures, overhead cams) and is not impacted by the level of anti-wear in SM/GF-4 oils. Classic engines with flat tappet cams with heavier valves and higher valve spring pressures do need the higher level of ZDDP anti-wear for cam/lifter/valve-train protection. For reference, it is easiest to indicate the ppm concentration of ZDDP in an engine oil by denoting the Zinc concentration in ppm since Sulfur, Phosphorus, and hydrocarbons can be present from other components.
ZDDP is a sacrificial substance that is critical to the anti-wear protection of metal surfaces within the engine. ZDDP's role as an anti-wear agent is most noteble at the cam lobe and lifter interface where the load exerted between the opposing surfaces (from the valve spring pressure) is great enough to breach the oil film, regardless of base oil viscosity. ZDDP is attracted to metal surfaces and is activated at those surfaces by heat and pressure. Without ZDDP, metal to metal contact between the cam lobe and lifter surface would occur and wear would increase dramatically at this interface, leading to component failure. As valve spring pressure and engine rpm's increase, the concentration of ZDDP needed in the oil must also increase for proper cam/lifter/valve-train protection. ZDDP is not a new technology, it has been used in engine oils since the 1930's. There are different types of ZDDP chemistries and it is important for an oil formulator to select the correct type(s) for the application.
API SM/ILSAC GF-4 oil is limited to 800 ppm of Phosphorus, which equates to approximately 850 to 900 ppm of Zinc. For moderately sprung flat tappet cams (hydraulic or solid), the minimum concentration of Zinc (Zn) for adequate cam and lifter protection is generally agreed to be 1200 to 1300 ppm Zn. For muscle cars (higher valve spring pressures), 1600 ppm Zn is considered to safely provide protection. For racing (higher spring pressures and higher rpm's), approximately 2000 ppm Zn is the typical target. For break-in of a new cam and lifters, 2000 to 2500 ppm Zn provides the proper level of protection (in combination with the molybdenum based cam lobe grease). Clearly, SM/GF-4 oils need additional ZDDP to properly protect classic car/hot rod/race car flat tappet cams and lifters and valve trains. Note that roller cams with high valve spring pressures are not immune either since the push rod ends and valve tips are subject to intense loading also and must be provided with sufficient anti-wear protection.
Neither GM EOS nor STP provide sufficient concentration of ZDDP in a single dose to raise SM/GF-4 oils to the proper level of protection for the classic flat tappet cam and lifter. Additionally, these products are in 15 and 16 ounce containers, which results in dilution of the engine oil. A much higher concentration of ZDDP is required to accomplish the job. Cam-shield(TM) is the most concentrated ZDDP additive available on the market (at least 30% more than ZDDPlus) so that the engine oil is not diluted and the performance integrity of the oil is maintained. Cam-shield(TM) was designed (by a race oil engineer at a major oil company) to be added to the user's favorite engine oil (conventional or synthetic) for either break-in or for normal operation (no other product is concentrated or flexible enough to be able to do this). Only 1/4 ounce is needed per quart of oil for normal operation (adds 800 ppm Zn to the 850ppm Zn in SM/GF-4 oil). For break-in or racing, only 1/2 ounce is needed per quart of oil (adds 1600 ppm). Cam-shield(TM) is a proprietary blend of primary and secondary ZDDP which gives full temperature range anti-wear coverage (start-up to operation). Cam-shield(TM)'s proprietary ZDDP has been proven in both street oils and at the highest levels of professional motorsports. Cam-shield(TM) is available in two sizes and clearly provides the best value available to consumers and businesses. The 4 ounce bottle ($13.95) treats up to 16 quarts (that's 3+ bottles of ZDDPlus = $29.85 +) and the 8 ounce bottle ($21.95) treats up to 32 quarts (that's 6+ bottles of ZDDPlus = $59.70). Cam-shield(TM)'s unique bottle allows the user to treat any size oil volume at oil change or top-up in between changes.
Note that neither diesel oil or racing oil are formulated for continual use in a street driven gasoline engine. Diesel oil is formulated with very high levels of detergency to combat soot. Detergency competes directly with ZDDP for the metal surface. Diesel is also generally formulated with primary ZDDP whereas gasoline oils require primary and secondary ZDDP. Additionally, due to different operating regimes (rpm ranges and loads), diesel oils and gasoline oils generally require different viscosity modifier polymers for proper bearing protection. Racing oils are formulated for the track and typically contain much lower levels of detergency and dispersancy than what is needed for a street driven gasoline engine, particularly a classic car or hot rod that may sit in the garage for weeks between runs.
Hope this was helpful.
Tim at Cam-shield(TM),
www.cam-shield.com
