Is it ok to put auto oil in a four stroke marine engine as long as the API ratings are met?

Question by tony: Is it ok to put auto oil in a four stroke marine engine as long as the API ratings are met?
I have a Yamaha 150 four stroke and it’s oil change time. I’ve heard you don’t have to use marine grade oil and all oil is the same as long as the API ratings meet or exceed the manufacturers recommendations. Is it ok to use “car engine oil” in my four stroke engine?

Best answer:

Answer by Ӝ
Yes. Use a good quality oil, such as Castrol, etc.

Add your own answer in the comments!

  1. Reply
    king_davis13 May 29, 2013 at 3:40 pm

    Yes as long as the ratings are at least to spec or better. Hope I have been helpful.

  2. Reply
    Richard C May 29, 2013 at 3:45 pm

    Yes, you can use any brand oil, however, some years ago the dealership I was working for was using oil from one of our suppliers, and found it didn’t meet the requirements for the warranty of one of the two major manufacturers engines we sold. We chose to use only their oil. Buying in larger quantities ended up at about the same price. So, check out the warranty requirements.

  3. Reply
    Derrick S May 29, 2013 at 4:12 pm

    To answer your question in short, NO. Marine grade engine oils are different from automotive oil. The difference being the anti-oxidation additive used in a “Marine” grade motor oil. API rating simply states that it meets an “American Petroleum Institute” requirement. It does NOT require/mandate that certain additives are included in the oil.

    Marine grade motor oils have additional additives which cars/trucks don’t need. There are additives to keep “High” moisture levels suspended in the oil without degrading the lubricating elements. Then there are additives for “Capturing” salt contaminates and minimizing metal erosion. Also, “Marine” grade motor oils have HIGHER levels of detergents (cleaners) to protect metal components from a higher ACID environment of marine engines. Also, the “HydroDynamics” of Marine grade oil is completely different from the “HydroDynamics” of an automotive grade oil.

    In short I’ve been through a class taught by the API about oils of all forms and have a “Certificate” to prove I know what I’m talking about. I teach boating safety, maintenance, trailering and several other areas of boating. I have to know what I’m talking about! Believe me before all of this training and info, I would be of the same opinion as everybody else in this forum. Knowledge is power and I’m just sharing my knowledge. Spend the little extra on “Marine” grade oil.

  4. Reply
    jtexas May 29, 2013 at 4:24 pm

    heed Derrick’s warnings.

    your engine will run just fine with automotive oil, but it won’t be as happy.

    a marine engine has a totally different mission than an automotive one. They typically sit around for weeks (or months), which is hard enough on machinery. Then you take it out and run it at constantly high RPMs, then put it way again.

    It doesn’t have a transmission to keep it in it’s “comfort zone” — it has to run high in the power band to push water out of the way and hold the boat up on plane. It’d be like driving your truck around in low gear, uphill, pulling a heavy load, all day long. There’s no loafing down the highway at 2300 RPM.

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