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  1. #1

    Default 4 stroke vs 4 cycle oil-what's the difference

    My Mercury 115mp EFI 4 stroke manual states I need to use 4 stroke oil. I chose synthetic Quicksilver 25W-40 but I noticed they also stocked a 25W-40 4 cycle oil. What is the difference?

  2. #2
    Admiral Dunaruna's Avatar
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    Quicksilver call all their 4 stroke oils '4 cycle'. The other oil you saw was probably a dino blend.

    99% of the boating population call a 4 stroke motor a '4 stroke' but the full descriptive term should be '4 stroke cycle'. Same thing with a 2 stroke, proper term is '2 stroke cycle'.
    Watch this space......................

  3. #3
    Ensign ebry710's Avatar
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    Yeah. It is defined as how many times the piston changed direction (up/down) before it completion a cycle. Each change of direction is a stroke.

    Two stroke only goes down once and up once to complete a cycle.

    A four stroke goes down to intake gas, up to compress gas, down to fire and up to exhaust.
    1987 Boston Whaler "Outrageous 18"
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  4. #4
    Supreme Mariner
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    Most 4 cycle outboards call for FC-W 4 cycle oil. This is a different oil than an auto would take. Your owners manual should point out the correct oil.

    I disagree slightly with the others, I believe "4 cycle engine" is the proper term and that "4 stroke engine" is a slang term.

  5. #5

    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    They are 4 and 2 cycle engines. FC-W 4 is the marine rating for 4 cycle oil.

  6. #6
    Supreme Mariner Silvertip's Avatar
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    There are no "engine terminology police". 4-stroke and 4-cycle can and have been used interchangably for ages, as have 2-stroke and 2-cycle. And not all four-strokes require FC-W oil. My Suzuki recommends conventional 10W-40 oil that meets current API specifications. If you buy Suzuki branded oil, it is marked FC-W however.

  7. #7

    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    Thanks for your response. That's the answer I was expecting. But I still don't understand why Quicksilver would market both? One bottle labeled 4 stroke and the other labeled 4 cycle both intended for outboard motor use.

  8. #8
    Supreme Mariner Silvertip's Avatar
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    As was pointed out, one may be a synthetic or a synthetic blend and the other is conventional oil. Both can be used if they are branded FC-W. As for the "cycle/stroke" thing -- it is meaningless and simply infers that the dude/duddette that designed the label was not paying attention to the what the other label indicated. No big deal. Different strokes for different folks.

  9. #9
    Ensign ebry710's Avatar
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    I went on goggle and searched vendor. From what I can see is that one is for conventional marine engines and one is for outboards.

    QUICKSILVER 4-CYCLE ENGINE OIL - 946ml [32fl oz][1 qt] 108LUB802837Q

    Quicksilver 4 cycle (or 4 stroke) marine engine oil keeps your engine cool when the going gets hot. Multi viscosity 25W-40 oil that you can run during the boating season. Used regularly, it will reduce engine wear and corrosion and protect against chemical attack, keep pistons clean, prevent rings from sticking and inhibit rust and sludge deposits

    QUICKSILVER 4-STROKE OUTBOARD OIL - 1 LITRE [33.8fl oz] 108LUB802833Q

    Formulated specially for 4 stroke outboards. Outboards typically operate at 5000-6000 RPM at wide open throttle, almost twice as fast as 4 stroke automobile engines. Normal automotive lubricants are not formulated to handle thse speeds. Quicksilver 4 stroke outboard oil contains special additives making it ideally suited for this application. They help reduce wear, scuffing and scoring, prevent the formulation of rust and sludge and inhibit the formulation of unwanted damaging foam
    1987 Boston Whaler "Outrageous 18"
    1989 Johnson 120 V4 VRO

  10. #10
    Supreme Mariner Silvertip's Avatar
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    So the Gents question (Why do they make both?) is still not answered. Since most four strokes at WOT run at 5000 - 6000 RPM, why would you market an oil that doesn't work well at those RPM -- which is what this advertising would imply!!!

  11. #11
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    Quote Originally Posted by Silvertip View Post
    So the Gents question (Why do they make both?) is still not answered. Since most four strokes at WOT run at 5000 - 6000 RPM, why would you market an oil that doesn't work well at those RPM -- which is what this advertising would imply!!!
    The short answer - MARKETING. If we were to have the oils analyzed, I suspect we would find that they are identical. The only difference is probably in the labelling. Why does Mobil 1 market a 5W-30 MOBIL-1 Full Synthetic AND a 5w-30 MOBILE-1 Full Synthetic SUV oil? Does an SUV need different oil than a pickup truck? Of course not. It is just marketing. Buy a good quality oil that has the correct viscosity and API rating and ignore the rest of the Marketing Hype on the label. You can put any label you want on a bottle of oil. Do you really think that Mercury, or Yamaha or any other engine manufactrurer makes their own oil? They buy oil that meets their specifications form an oil company and put their label on it. My 2 cents and probably worth exactly what you paid for it.

  12. #12
    Ensign ebry710's Avatar
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    Quote Originally Posted by Silvertip View Post
    So the Gents question (Why do they make both?) is still not answered. Since most four strokes at WOT run at 5000 - 6000 RPM, why would you market an oil that doesn't work well at those RPM -- which is what this advertising would imply!!!
    OK. it is marketing. The logic for saying this engine oil is use for WOT throttle, while this oil is designed for operating at 2-3000 rpm has been used for years. Castrol Motor Oil used that to sell their oil by saying "our oil is designed to handles today's new high out put engines"....)not exactly what they said, but close).

    The question becomes, and an effective question, knowing this information do you buy an oil designed for grandma's 4 stroke engine or do you buy the one designed to operation in the environment of a wake board boat where you are looking good and wearing your aviator glasses.
    1987 Boston Whaler "Outrageous 18"
    1989 Johnson 120 V4 VRO

  13. #13
    Commander
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    Honda has been in the 4 stroke engines longer than most other makers and they still to this day recommend auto oil for all thier engines. Do you think Honda makes their own oil?, I dont think so, ay more than Mercury makes their own branded oil. I don't think I have ever 25-40 oil except maybe in Diesel oil, then again I have never looked for it, much less use it.

  14. #14
    Captain JUSTINTIME's Avatar
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    Default Re: 4 stroke vs 4 cycle oil-what's the difference

    Honda has their own oil now, of course not made by them

    reason why quicksilver has 2 oils, because it is mercury and they sell i/o's and outboards

    outboards run a higher rpm than i/o's
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