OK, here are some excerpts from the article by Hib Halverson that I scanned in. There will be a Part 2 to this article in the next issue. By the way, if you haven't checked out
Corvette Enthusiast yet you might want to. Not so :quote:so technically lightweight and full of fluff:quote: as the other mags.:thumbs:
"The most common EP additive in automotive engine oils is zinc dialkyldithiophosphate (ZDDP), a family of coordination compounds of zinc and dithiophosphoric acid which, in longer-chain, molecular derivatives, easily dissolve in engine oils. Known more commonly as "zinc dithiophosphate" (ZDP), "zinc phosphate", or quite incorrectly, just "zinc", this compound was initially added to oil in the 1940s as an anticorrosive/antioxidant. Later, it was discovered to be an excellent extreme pressure lubricant.
When subjected to heat present at the lobe/lifter interface, ZDP decomposes into alcohol, zinc, sulfur and phosphorous. The alcohol evaporates and the zinc mostly washes away, leaving sulfur and phosphorous to combine with iron molecules on the surface of the cam lobe to make iron sulfide and iron phosphate, the two compounds which perform EP lubrication.
"The 'di-thio' in 'zincdithiophosphate' means for every phosphorous there are two sulfur molecules," Red Line Synthetic Oil Corporation's Vice President and top petrochemical engineer, Roy Howell, told Corvette Enthusiast. "Sulfur is probably more important than zinc and phosphorous.
"The (cam and lifter) wear surfaces are rich in iron and sulfur with a lesser amount of phosphorous. The ZDP decomposes into a soft, thin film of iron sulfide and iron phosphate which prevents iron adhesion, or welding. The zinc doesn't do much. If you look at photomicrographs of cams and lifters, there's hardly any zinc coating, but there's a lot of iron sulfide coating and some iron phosphate coating.
Oil blending data prior to the early '90s is difficult to acquire, but our research revealed that mass-marketed engine oil typically used by consumers from the late 1950s to the mid-'70s had enough ZDP to result in around 800 parts per million phosphorous content or "phos" as some engineers say. In the early 70s, "finger followers" were introduced in some single overhead camshaft (SOHC) engines. They presented a durability problem, initially thought to be caused by insufficient EP lubrication. In response, from the late '70s to the mid-1980s, phosphorus in most oils climbed to about 1000 ppm. Ironically, as experience with finger follower engines grew, it was eventually determined that, due to the location of the valvetrain in the engine, blowby-driven corrosion was affecting the durability problem more than insufficient EP lubrication.
In the late 80s/early 90s, the oil industry began to decrease phosphorous, back towards 800 ppm because: 1) extra ZDP for finger followers proved unnecessary and alternative methods
- improved materials, other additives were found to enhance durability, 2) OEs were converting to roller lifters which required less EP lubrication, 3) OEs wanted to improve the longevity of emissions controls and 4) historically, as far back as the mid-'50s, 800 ppm phosphorous provided good durability of flat tappet cams and lifters in production OHV engines.
Inevitably, the Federal government began to "stir the pot." By the late '80s, the Federal Environmental Protection Agency (EPA) decided that phosphorous released by small quantities of oil burned by the engine gradually deactivates or "poisons" the reactant which enables a catalytic converter (some call them "catalysts" or just "cats") to convert certain exhaust gas components to less toxic substances. Once that happens, the cat ceases to be effective.
The EPA, deciding it was better for us to have expensive, long-life cats instead of more frequent replacements of "short-life" cats, offered car companies incentives for implementation of more durable catalysts. Politicians and EPA's mandarins figured the OEs would pressure the oil industry to scale back use of ZDP, thereby reducing phosphorous and preventing the premature demise of hundreds of millions of catalytic converters. This was a slow ramp-up, starting around the '80s at 50,000 miles. The current cat life requirement is 120,000 miles, and it goes to 150,000 miles for model year 2009.
Sure enough, car companies, which by the mid-'90s expected to be using either roller lifters in OHV engines or less highly-loaded, direct-acting flat tappets in OHC engines, convinced big oil to reduce phosphorous to extend cat life. Its leverage was the purchase of millions of gallons of oil a year to factory-fill their engines and its recommending types of oils in owner's manuals.
In 1987, American car companies, along with Japanese manufacturers assembling cars in the U.S., formed the International Lubricant Standards and Approval Committee (ILSAC). One of ILSAC's goals was to enact standards which would gradually reduce phosphorous in engine oils carrying its and API's Service certifications.
ILSAC GF-1 ("GF" meaning "gasoline fueled") became effective in 1992. API followed with an "SH" version of its "Service" grades, which until recently, were more familiar to consumers. GF-1 was the first oil standard with a phosphorous ceiling - 1200 parts-per- million (ppm). API Service SF and prior, didn't regulate phosphorous. This first "max-phos" number was irrelevant, because other than racing, diesel and other special purpose engine oils that were not certified anyway, most oil bought by Vette owners had way less than 1200 ppm phosphorous.
While GF-1 allowed up to 1200 ppm phosphorous, few of the GF-1 5W30s or 10W30s Corvetters used back then had more than 1000 ppm. So-called "racing oils" held phos to 1100-1300 ppm. Most oils purchased by consumers ranged 800-1000 with a majority around 800, a figure which nearly half a century of research and experience proved was adequate to lubricate the vast majority of stock engines with flat tappet or finger follower valvetrains and even some with mild, aftermarket, high-performance cams. Oils with viscosity higher than 10W30 were exempt from the phos limit.
In 1996, GF-2 was issued, and in 2002, ILSAC/Oil released GF-3, API Service SJ is comparable to GF-2, and SL corresponds to GF-3. All of these mandated 1000 ppm max phos, but by then, most engine oils with viscosities 10W30 or less were about 800, with perhaps a few during the GF-3 period, getting down between 600 and 800 ppm. Viscosities higher than 10W30 continued exempt from the phosphorous limit.
Where decreasing ZDP content first caused trouble was with engines having aftermarket, flat tappet camshafts with aggressive profiles, racing valve springs or high-ratio rockers - parts which raise load at the lifter/lobe interface to over 200,000 psi. Such valvetrains required break-in procedures incorporating special additives, such as Crane Cams' "Superlube" or Red Line's "Engine Oil Break-In Additive," both of which have additional ZDP, along with other components, such as molybdenum disulfide. Once break-in was complete, these engines needed oil with 1000-1200 ppm phosphorous. As we will learn in Part 2, not all users of these cams were aware of this need, and some who were aware, disregarded it. With CF-1 through GF-3 and SJ to SL, phosphorous regulation was a maximum limit, not a minimum requirement. As long as oil companies didn't exceed that, they could put any percentage of ZDP in the oil necessary for it to pass the battery of tests required for certification.
GF-4 came in 2005 and was matched by API Service SM. GF-4 required oils with viscosities of 10W30 or lower to hold phos above 600 ppm, but below 800 ppm. This was the first specification which drove any significant change in oil blends, because previously, most had been at 800-1000 ppm, at or below any prior phosphorous ceiling and now, phos was held in a range. Viscosities higher than 10W30 continued to exempt from phos limits,
GF-5, due for introduction for the 2011 model year is not yet finalized, but ILSAC/Oil Chairman Olree, told Corvette Enthusiast that he believes GF-5 will have the same phosphorous specification as GF-4."
