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Type of Oil to Use-gctid828240

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    Type of Oil to Use-gctid828240

    Recently purchased a '96 2452 ciara Express with a 2001 mercrusier 350 in it. Motors in great shape low hours I don't recall exactly but I believe around 500.

    My question is what type of Oil should I be using in it? Heard lots of theorys currently have Rotella 15W30 in it. This a good mix or should it be different? For what it's worth the boats in Lake Superior cold water.

    Thanks for the help.

    Welcome to the forum!

    I would think that 15W30 is a little on the light side. I think Mercury recommends 20W40.

    Most good 15W40 synthetics should be fine.

    With oil you are going to get a wide variety of answers, everybody has their favorite.
    1987 3818 Hino 175
    "Knotty Girl"
    Prince Rupert B.C.


      Agree with 15/40 minimum
      Edmonds, WA
      "THE FIX" '93 2556
      Carbureted 383 Vortec-Bravo II
      The Rebuild Of My 2556
      My Misc. Projects


        Thanks guys, I'll do a little more research but start it with 15W40.


          even in todays world of new and improved? multi-vis oils, GM still recommends straight 30wt in their marine engines.... but people still take it upon themselves to use a multi-vis oil, and without any problems that can be definitively blamed on the oil... I use 30wt, with additives.

          since they removed the zinc from motor oils, it has lost a bit of its lubricating qualities, and these newer oils are extremely hard on the cams of the older 454 engines, unless additives are used.

          NU LIBERTE'
          Salem, OR

          1989 Bayliner 2556 Convertible
          5.7 OMC Cobra - 15.5x11 prop
          N2K equipped throughout..
          2014 Ram 3500 crew cab, 6.7 Cummins
          2007 M-3705 SLC weekend warrior, 5th wheel
          '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
          Heavy Equipment Repair and Specialty Welding (RETIRED)


            Yes very true about the lack of zinc and phosphorus causing accelerated wear. The synthetics still have high levels of zinc, just be sure to use an actual break in oil with any new engine with flat tappet cam and lifters.

            To Malyu007 just be sure to use synthetic if you are going with 15w40.

            A conventional 15w40 is a 15 weight oil that has had additives added to make it "act" like a 40 weight oil when hot. The problem with this, is once the additives break down, you are left with a 15 weight oil.

            Synthetics are built as a 15w40 for instance, and will not break down over time, they will sometimes thicken however due to contaminants.

            The oil debate can and will go on forever, but these are the basics.
            1987 3818 Hino 175
            "Knotty Girl"
            Prince Rupert B.C.


              Fwiw, I used either the Mercruiser or Quicksilver semi synthetic in my 4.3's and 470's before. I found that the Merc/Quick oil dumped heat better after coming off a plane with the 470's than other oils I tried so I stayed with it when I repowered to the 4.3's.
              P/C Pete
              Edmonds Yacht Club (Commodore 1993)
              1988 3818 "GLAUBEN”
              Hino EH700 175 Onan MDKD Genset
              MMSI 367770440


                Older Caterpillar crawler tractors used straight 30w throughout the tractor, engine, torque converter, transmission, final drives (equivalent to extreme duty rear end), hydraulics, steering clutches and brakes. They would last for 10,000 hours or more using that oil. You could run them WOT loaded all day long. As Centerline2 commented GM recommends 30w. I am a factory trained Kawasaki commercial engine mechanic. They recommend 30w in liquid cooled engines until operating in very hot climate, then they recommend 40w. The air-cooled engines which have larger piston to cylinder wall clearances they start out with 30w in cold climate, 40w in moderate climate and 50w for hot climate. I am stating this to explain why I find it difficult to understand why 40w should be run in a gasoline fueled liquid cooled engine with virtually unlimited cooling capacity. I am not a marine engine expert so maybe someone could fill me in on what I am missing. By the way air-cooled aircraft engines commonly use 40w or 50w and they run at 75% - 80% maximum power output for hours on end. So I am puzzled. Help me.
                Newport, Oregon
                South Beach Marina
                1986 3270 with twin 110 HP Hino diesels. Name of boat "Mr. Darcy"
                Past work history: Prototyping, tooling, and repair for Reinell,. General fiberglass boat repair starting in 1976.
                Also worked as heavy equipment mechanic, and machinery mechanic for over 30 years.