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OT: Oil Mixup for mower

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  • OT: Oil Mixup for mower

    Sometimes helping the neighbor becomes tricky...
    Would using 2-cycle motor oil (the pure oil, no gas mixed in) as the oil in a 4-cycle engine cause damage? Mower was used for 30-45 minutes before the error was discovered... leading to my second problem

    The engine is a 6.5HP Briggs & Stratton vertical shaft mounted on a Sears 944 series 21" model power mower. I cannot locate any more info on either the engine or the mower. The mower is a walk-behind, tho with power to drive the front wheels (belt & pulley arrangement). The oil drain plug is steel that accepts a 3/8" socket extension to loosen it. None of the usual approaches work and I fear cracking the aluminum sump housing if I get too ambitious.
    Pretty much left with pumping the oil out the fill port. Do I pump out & replace with 4-cycle or pump out, flush, replace or...

  • #2
    It probably hasn't done any damage. I wouldn't flush it out. Just pump it out or turn the mower over and let it run out. Refill with the proper oil and you should be good to go. Don't even try to remove the drain plug.
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

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    • #3
      Sae30 is often used in those motors, no oil filter, so a non detergent oil. I see no harm in pumping the oil out the filler in those simple engines.
      Maybe stick a magnet down there to pick pick up any shavings if your worried about that.

      Sent from my SM-G950U1 using Tapatalk

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      • #4
        If it's the appropriate weight, you could just leave the 2stroke oil in there. Only thing is, it won't have any detergent (dispersant) action. But you should replace it - assuming it's *not* castor-based oil (wonderful smell but a pain to clean up) any of it left in the crankcase will mix fine with regular oil.

        The big difference between motor oil and modern 2stroke oils is the latter have low ash content (so as not to foul spark plugs) and low smoke when they burn. The oil you used is probably synthetic for extra-clean burning and superior lubrication. And non-detergent.

        -js
        There are no stupid questions. But there are lots of stupid answers. This is the internet.

        Location: SF Bay Area

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        • #5
          Originally posted by RB211 View Post
          Sae30 is often used in those motors, no oil filter, so a non detergent oil. I see no harm in pumping the oil out the filler in those simple engines.
          Maybe stick a magnet down there to pick pick up any shavings if your worried about that.

          Sent from my SM-G950U1 using Tapatalk
          I've used and maintained a lot of small engines over the years, Tecumseh, B&S, Kohler, Honda, not one of them has a manufacturer's recommendation to use non-detergent oil.

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          • #6
            Originally posted by cameron View Post
            I've used and maintained a lot of small engines over the years, Tecumseh, B&S, Kohler, Honda, not one of them has a manufacturer's recommendation to use non-detergent oil.
            My Generac (Tecumseh motor, I think) specifies non-detergent.

            -js
            There are no stupid questions. But there are lots of stupid answers. This is the internet.

            Location: SF Bay Area

            Comment


            • #7
              Originally posted by cameron View Post
              I've used and maintained a lot of small engines over the years, Tecumseh, B&S, Kohler, Honda, not one of them has a manufacturer's recommendation to use non-detergent oil.
              Detergent oil is for pressurized oil systems that go through a filter. These simple engines use a splash oil system. They probably don't mention it because it's irrelevant to them. In my opinion, you want the junk to stay at the bottom, not be suspended in the oil.

              Sent from my SM-G950U1 using Tapatalk

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              • #8
                Originally posted by RB211 View Post
                Detergent oil is for pressurized oil systems that go through a filter. These simple engines use a splash oil system. They probably don't mention it because it's irrelevant to them. In my opinion, you want the junk to stay at the bottom, not be suspended in the oil.

                Sent from my SM-G950U1 using Tapatalk
                They do mention it. They all specify the oil to be used in the engine. They run SC,SD,SE, SF,SJ,SH, depending on when the engine was made.

                Perhaps you haven't seen the inside of an engine that had been run for a few years on non-detergent oil.

                You should inform the engine manufacturers of your opinion, they've probably been doing it all wrong.

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                • #9
                  As far as oil changes through the filler. I have a Honda powered push mower and that engine doesn’t have a drain plug. When it is time for an oil change the gas valve gets shut off to the carb and the mower tipped on its side until the oil runs out, no pump needed.

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                  • #10
                    Originally posted by Jim Stewart View Post
                    My Generac (Tecumseh motor, I think) specifies non-detergent.

                    -js
                    What model of Tecumseh, and what year was it made?

                    Some of the engines I've dealt with have single grade SAE 30 oil recommended for summer use, but not non-detergent SAE 30.

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                    • #11
                      Any oil would be better than none,,,????? but it would be wise to drain it and put in the proper slick.
                      _____________________________________________

                      I would rather have tools that I never use, than not have a tool I need.
                      Oregon Coast

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                      • #12
                        Originally posted by cameron View Post
                        I've used and maintained a lot of small engines over the years, Tecumseh, B&S, Kohler, Honda, not one of them has a manufacturer's recommendation to use non-detergent oil.
                        I was wondering about what RB said also. I put non detergent oil in an old 2.5 HP Briggs along time ago and it really gunked up the insides. Never used it again, always detergent.
                        I doubt the 2 stroke oil did any harm. It keeps everything lubricated in a 2 stroke and they run at a lot higher r's than the brigs 4 stroke does.

                        JL.............

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                        • #13
                          From the horse's mouth:

                          https://www.briggsandstratton.com/na...-capacity.html

                          When choosing lawn mower oil, use a high quality detergent oil classified as "For Service SF, SG, SH, SJ" or higher. Do not use special additives.
                          https://www.bobistheoilguy.com/forum...&Number=483370

                          https://www.ferrismowers.com/na/en_u...my-engine.html

                          https://www.mytractorforum.com/44-sm...-oil-good.html

                          Use non-detergent oil for your lathe or mill - unless it has a gas engine
                          Last edited by PStechPaul; 06-13-2019, 11:31 PM. Reason: link
                          http://pauleschoen.com/pix/PM08_P76_P54.png
                          Paul , P S Technology, Inc. and MrTibbs
                          USA Maryland 21030

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                          • #14
                            Originally posted by cameron View Post
                            What model of Tecumseh, and what year was it made?

                            Some of the engines I've dealt with have single grade SAE 30 oil recommended for summer use, but not non-detergent SAE 30.
                            It's been years since I looked at the manual, but I believe you're right. It wasn't non-detergent specified, it was single weight SAE30 - IIRC, it said multigrade didn't hold up at the higher temperatures of an aircooled stationary engine.

                            -js
                            There are no stupid questions. But there are lots of stupid answers. This is the internet.

                            Location: SF Bay Area

                            Comment


                            • #15
                              Originally posted by cameron View Post
                              I've used and maintained a lot of small engines over the years, Tecumseh, B&S, Kohler, Honda, not one of them has a manufacturer's recommendation to use non-detergent oil.
                              Unless there is a removable FILTER, there is no reason to use detergent oils.

                              Think!

                              Detergent means that contaminants are held suspended in the oil. There is no reason to do that if the oil does not pass through an efficient filtration device.

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