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  1. #1

    Switching oil on Polaris slt750

    Hey guys, sorry about all the questions. I know everyone has there opinions on what to do with oil but right now I’m running non synthetic oil and I just bought a gallon of pennzoil synthetic oil. Can I just put the synthetic in the tank or would that cause a problem? Also will the synthetic make the motor run better?


  2. #2
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by Crerar20 View Post
    ... what to do with oil but right now I’m running non synthetic oil and I just bought a gallon of pennzoil synthetic oil.

    Can I just put the synthetic in the tank or would that cause a problem?

    Also will the synthetic make the motor run better?
    Except for a specific type of racing oil (caster oil?) you can generally mix 2-stroke oils.

    My own practice when switching 2-stroke oils was to run the old oil level down as low as I dared in the oil tank, then refill with the new oil.

    You are correct about there being many opinions about oils!


    My perspective

    Synthetic oil will not make a 2-stroke engine ‘run better’. I also have my doubts about synthetic 2-stroke oil improving engine longevity. Other factors and the owner’s engine care regime are more influential on engine lifespan.

    The primary ‘point’ of synthetic oil is high temperature stability and longevity in 4-stroke engines, where the oil is recirculated within the engine and re-used endlessly for months and many running hours (or thousands of miles in a road vehicle). Synthetic 4-stroke oil resists degradation and high combustion temperatures.

    In a 2-stroke engine the 2-stroke oil dribbles into the air intake as the engine runs, and then the oily mist swirls around in the crankcase for ‘a while’. Some of the oil collects on the interior surfaces and flows into the spinning crankshaft bearings, lubrication of which is a primary purpose of the oil. The turbulent oily mist also sprays onto the cylinder bore surfaces below the piston, lubricating the piston movement.

    At higher RPM and engine loads the oily mist in the vortex of crankcase air is drawn upwards into the combustion chamber with each piston cycle, where the oil is then burned along with the fuel. The (perhaps only partially) burned oil is expelled with the exhaust flow and leaves the engine. This is why 2-stroke engines need a constant feed of fresh oil into the air intake, to replace the oil that gets consumed as the engine runs.

    What you want in a good 2-stroke oil is excellent metal coating properties, where the oil tends to ‘coat’ the metal surfaces and provide good lubrication of the moving parts.

    When the engine is shut down and left sitting for weeks or months at a time, the oil film needs to stay in place and protect the steel engine internals from rust. Remember the exhaust waterbox holds liquid water after riding, and that moisture will work it’s way through the exhaust manifold towards the engine while the machine is parked. The crankshaft and the bearings inside the engine are all steel.

    When the engine is running the oil mist gets drawn into the combustion chamber, where you want the oil to burn cleanly and completely. High quality conventional 2-stroke oils should do this.

    My view is that synthetic 2-stroke oil is ‘ok’ but my experience is that the metal coating properties are not particularly good, especially during longer term storage. And the synthetic oil tends to not burn as cleanly, leading to more black oily residue in the exhaust.

    Years ago I used to use Amsoil synthetic 2-stroke oil, and eventually I changed to a high grade conventional 2-stroke oil.

  3. #3
    Thanks for that great information. But I already bought a gallon of the synthetic. Should I just throw it away or can I use it and just go back to regular later?

  4. #4

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    You should be fine switching, but you should not take switching lightly. Like K447 said, run down your current oil, or drain it out with a siphon and put it in a different boat, then add the new stuff.

    He's 100% right about the oil, you want an expensive, high quality oil because it'll leave a good film on your engine parts, will stay after it sits for a while, and won't cause a lot of carbon build up. I use Klotz Racing Pre mix since I converted all my skis to premix. It's a thicker oil that won't actually work in injectors, and it has benol so it leaves a solid protective film on everything. But it's also around $50 a gallon.

    I always think the added protection of spending money on nice oil is better than having to deal with crank damage. The only problem I ever really have with any of my skis is the rear cylinder on one of my pros cold seizing when the waters cold. Otherwise I usually just wear out the bores from riding them so much and have to sleeve and bore. Though that doesn't really apply to the pros because of the nikasil.

    If you're switching to a cheap oil, don't do it. If you're bouncing between cheap oils, don't do it. If you're getting better oil, go for it and stick with it.

  5. #5
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    Personally I would not mix them at all. I would get the one oil out of the tank and oil lines then put in the other stuff...but that's just me.

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