It seems that the consensus of knowledgeable commenters is that oil with a CJ-4 API designation is the right thing to use on vintage performance engines because it has enough of the zinc additive for wear protection of flat tappet valve trains with heavy springs. However, the 15-40 Shell Rotella I bought was labeled API CJ-4/SM. Isn't SM a modern gas engine designation that limits the amount of zinc additive? How can oil satisfy both CJ-4 and SM designations?
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Re: Shell Rotella oil question
Interesting thought. Doesn't SM designated oil limit the amount of zinc in oil to levels lower than CJ-4??
I'm on the edge of my seat.....
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Re: Shell Rotella oil question
Here is a recent used oil analysis of Rotella T, looks fine as to ZDDP content. Not sure about what the SM designation means.
Big Tanks In the High Mountains of New MexicoComment
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Re: Shell Rotella oil question
From the API guide http://bit.ly/10x8FY4 SM CURRENT For 2010 and older automotive engines. I believe the key word is olderDick WhittingtonComment
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Re: Shell Rotella oil question
Patrick,
I believe the first designation (CJ) takes presidence, SM is a secondary designation meaning it's acceptable use in gasoline engines and the oil meets at least API specs for SM.Comment
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Re: Shell Rotella oil question
The answer to my question was contained in the thread by Michael Funk that appeared at the top of the "related threads" listing automatically appended to this thread. In one of his comments Duke Williams states that the phosphoros spec in the SM designation that limits ZDDP carries an exemption for oils with a winter viscosity of 15 or greater. Therefore, the ZDDP required by CJ-4 does not prevent an oil from satisfying the SM if it is a 15w-40 oil. However an 10w-30 SM oil could not also satisfy CJ-4. While unlike an SM 10w-30 oil, an SM 15w-40 oil is not prohibited by the spec from having a high ZDDP content, there is no reason to believe it actually has a higher ZDDP content unless it is formulated to satisfy another requirement such as CJ-4 that demands a higher ZDDP content.Comment
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Re: Shell Rotella oil question
Duke,How bout this? I've always made efforts to always find 10W30 Rotella T; does it not have enough ZDDP(not as much as the 15W40) to protect my flat tappet Corvette cams?Comment
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Re: Shell Rotella oil question
Get the Joe Gibbs BR oil for break in and Hot Rod Oil after break in.It has all the zinc and phos needed plus additives to stay stuck on the parts while setting around.Comment
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Re: Shell Rotella oil question
"Thus, a 15W-40 CJ-4 can also carry SM as a secondary rating because the 15W winter rating exempts it from the .08% phosphorous limitation in the SM specification".
Dick, the above sentence is a quote of from Duke Williams comment (#10) to Michael Funk's October 2007 thread "rotella oil question and flate tappet cams???" listed below in the Similar Threads listing.
5W oils can certainly meet the CJ specs but they cannot meet the SM specs simultaneously.Comment
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Re: Shell Rotella oil question
William,
As long as it meets API CJ-4 it is fine.
JoeComment
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