I am not saying that you should use 0W/40 or that a low ZDDP oil is
OK for flat tappet engines. All I am saying is that the API believes
that the low ZDDP oil is OK for flat tappet engines, or at least they
did when they came out with the latest standard. Therefore, they
consider or considered each classification to be backward
compatible. Thus a manufacturer claiming SJ and SM compatibility is
just stating what the standard already says, which is that all SM oil
meets the SJ standard. It's like brake fluid, before the silicone
stuff came into the picture. The container would say "DOT 3/DOT 4"
because all DOT 4 met the DOT 3 criteria. BTW, diesel oil has a
whole different set of API classifications, as shown in the link I
provided. What I am saying is not controversial. I am just giving
an explanation for a manufacturer making the claim of meeting
multiple standards.
-Steve Trovato
strovato@optonline.net
At 09:08 AM 9/23/2009, Paul Hunt wrote:
>That's just not correct, it's like saying if 0W/40 fully synthetic
>is right for high-performance modern engines it must be good enough
>for ours, which is definitely *not* correct. There is more than
>enough evidence out there from *owners* that modern, low ZDDP oils
>cause problems, see
><http://www.ttalk.info/Zddp.htm>http://www.ttalk.info/Zddp.htm and
><http://lnengineering.com/oil.html#Z13>http://lnengineering.com/oil.html#Z13.
>The fact that you can quote sources that say SM is fine, and I can
>quote others which say it isn't, just goes to show how confusing the
>whole subject is. It is a fact that modern Diesel oils have a
>higher level of protection, and so conform to the earlier petrol
>grades, precisely because Diesel engines need more protection for
>the little ends than SM can give, similar to flat-tappet engines.
>
>PaulH.
>----- Original Message -----
>
>API motor oil guide says "For automotive gasoline engines, the
>latest engine oil service
>category includes the performance properties of each earlier
>category. If an automotive
>owner's manual calls for an API SJ or SL oil, an API SM oil will
>provide full protection."
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