I found several references that the common Sulphur-Phosphorus EP additives decompose rapidly starting at about 250F. Is this true? If so, this makes me wonder what good a PAO synthetic base oil would be with an S-F add pack. I'm struggling to determine what manufactuers use which EP additives so some insight on that would be enlightening as well.
EP Additives, Thermal Limits
- Thread starter Jim Allen
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MolaKule
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Look at the "Question of the Day" thread and look for information on anti-oxidants and metal deactivators.
And in the "Interesting Articles" thread search on "Gear."
Wow! Mega-kudos, Mr. Kule! I'm definitely not worthy. Those references are a heapin' helpin' of info that will take some time to consume and digest. In scanning them, however, I did not see any references to the sulpur-phosphate EP additives decomposing at high temps (250-275F). Is this true? If so, wouldn't this be the limiting factor in an oil, somewhat negating the benefits of a PAO synthetic. If that's the case, what would be a better additive to use? If not, please correct my thinking.
Jim,
Eaton-Fuller (the the maker of the most widely used power train components in road transport) carried out extensive field tests in the late 1980s on GL1 and GL5 synthetic gear lubricants before endorsing them. They have been a factory fill for the last several years in some applications
Some of their comments follow;
"The traditional Sulfur-Phosphorus additive package chemically activates rapidly above 230F
Components should not be operated consistently at temperatures above 250F. Intermittent operating temperatures to 300F however do not harm the transmission. Operating temperatures above 250F increases the lubricant's oxidation rate and shortens its effective life"
"A poor additive package in a synthetic oil offers NO advantage over a thermally stable additive in petroleum base stock"
"Lubricants that have passed Eaton's qualifications have demonstrated that the total lubricant package give excellent perormance over a 250 000 miles change interval"
I have used synthetic lubricants in these applications since 1992 and at 650 000 miles OCIs
Doug
Eaton-Fuller (the the maker of the most widely used power train components in road transport) carried out extensive field tests in the late 1980s on GL1 and GL5 synthetic gear lubricants before endorsing them. They have been a factory fill for the last several years in some applications
Some of their comments follow;
"The traditional Sulfur-Phosphorus additive package chemically activates rapidly above 230F
Components should not be operated consistently at temperatures above 250F. Intermittent operating temperatures to 300F however do not harm the transmission. Operating temperatures above 250F increases the lubricant's oxidation rate and shortens its effective life"
"A poor additive package in a synthetic oil offers NO advantage over a thermally stable additive in petroleum base stock"
"Lubricants that have passed Eaton's qualifications have demonstrated that the total lubricant package give excellent perormance over a 250 000 miles change interval"
I have used synthetic lubricants in these applications since 1992 and at 650 000 miles OCIs
Doug
Could not have said better
bruce
bruce
OK, so the consensus thus far is that the S-P packages tend to break down at high temps. What formulation does not? What are the the better syn gear oils using? Most of what I have seen so far is S-P, regardless of base oil. There are some calcium-boron-moly packages. LE has some stuff call Almasol and Monolec. Vanderbilts has several Vanlube EP concoctions. Castrol has something called Molub alloy. There are others. Many just give a brand name and do not describe what's in the package.
IMHO Chevrons Borate Delo gear is one of the best with Good base stock and robust additive package and the buffering of the borate it is one of the best and will run with the syns.
bruce
bruce
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