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  • #16
    From my M3 Supplementary Owner's Manual

    Click image for larger version

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    1990 M3

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    • #17
      it seems that instead using oil designed for high performance car engines, people are using oil designed for slow speed diesel truck engines. sooo...what is behind this fad? is there any science?
      75 M2
      88 M3

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      • #18
        I think it has to do with ZDDP levels. Their conventional diesel oil has ZDDP levels ~1450 ppm. Their T6 synthetic is ~1180 ppm. This is not the full story however. Rotella Diesel oil has less wear properties and should not be used in high performance engines like ours. It has something to do with "Load Carrying Capacity / Film Strength" which correlates to protection properties. All a bit above my pay grade honestly.

        I figure diesel engine oil is formulated for diesel engines and my OCD won't allow me to put that oil in my S14.
        1990 M3

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        • #19
          Would love to see the oil pressure logs vs rpm for various weights since everyone seems to use 50w or higher, compared to the spec 40w.

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          • #20
            Originally posted by ADA///M View Post
            I believe 15w-40 was the spec for our cars.

            My car is relatively stock, so I run a 0w (or 5w)-40. Usually Shell Rotella.

            Not sure why we'd want anything thicker unless the engine wasnt stock internally or had other issues to overcome.

            T6 I take it?
            Do you add any additives?
            Thanks!

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            • #21
              Originally posted by ADA///M View Post
              . . . compared to the spec 40w.
              The spec is 15W40 OR 15W50 per the supplemental manual.

              1990 M3

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              • #22
                Swepco 15W40 since the engine rebuild in 2010. So far so good! Here's the oil analysis you can see the Zinc levels...
                Attached Files

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                • #23
                  Not many miles on the Swepco between changes. Only thing worth looking at are the wear metals. Swepco must blend the oil on the thin side. 12 cSt is the minimum for 40.

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                  • #24
                    In the past I too used Liqui Moly 10w-60 for my stock M3. I was getting some brief tensioner rattle upon start up and I switched to Liqui Moly 10w-40. In both cases I always use either Ceratec ( every third oil change) or Liqui Moly Oil Additive ( in between use of Ceratec).

                    With the 10w-40 in my S14 the tensioner rattle has disappeared.

                    Could be time for a new tensioner too

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