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Thread: Synthetic or semi-synthetic?

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    Rocky ST's Avatar
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    Synthetic or semi-synthetic?

    Now regarding the clunk I was experiencing going into 1st gear,I'm going to try changing the oil/filter,even though I was told this was done just before I bought it.
    now my question is this,I have always used semi-synthetic in all the bikes I've owned in the past,however a couple of membership suggested putting fully synthetic in it? Being UK based,which should make no difference,like I say I've always used Semi?
    Your thoughts please

  2. #2

    Re: Synthetic or semi-synthetic?

    IMHO semi synthetic is simply a marketing ploy allowing them to take a cap full of synthetic and add it to normal oil and call it semi synthetic, and then jack the price up for specialty oil.
    Run Diesel oil (heavy duty engine oil).

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    Site Supporter Dale_I's Avatar
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    Re: Synthetic or semi-synthetic?

    A lot of guys are using Chevron Delo 400, which is a para-synthetic (semi-synthetic). Not really much more expensive than organic.
    #5341

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    Site Supporter RaYzerman's Avatar
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    Re: Synthetic or semi-synthetic?

    Clunking into first can be due to other things. Suggest flush and bleed the clutch so you have maximum engagement. Check the brass bushing in the clutch lever to see that it is not worn, thus not enough master cylinder stroke. Ensure you're pulling the lever all the way to the bar. Wait an extra second before shifting.
    It's probably worse when cold because the clutch is dragging with the cold oil.
    Ray

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    John Heath jfheath's Avatar
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    Re: Synthetic or semi-synthetic?

    I can tell the difference between full and semi synthetic, just from how the engine feels and sounds. I always use fully synth. Preferably Shell Ultra.

    Mine clunks changing gear sometimes, recently. When it decides it is going to do this, I pull the clutch lever in and leave it a fraction before changing gear, which seems to work.

    I'm guessing that there's a tiny air bubble in the clutch system. It can wait until I have the fairing off again.

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    SMSW's Avatar
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    Re: Synthetic or semi-synthetic?

    Not to hijack this thread but can someone explain exactly what semi-synthetic oil is? Yes, I've read the label at oil displays - its a "blend of the finest synthetic stocks" with old, recycled oil. (I've corrupted what the label says a tad.)

    But, are there any regulations regarding % of synthetic oil to recycled oil? Any regs regarding what new oil is used in the blend vs. recycled?

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    Site Supporter Don B's Avatar
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    Re: Synthetic or semi-synthetic?

    I'm not sure what the basis for this is, or how true it may (or may not) be but I read or heard several years ago that a high mileage engine that has always used organic oil it is best NOT to switch to full synthetic.
    IIRC, the reason for this is the seals and gaskets are more likely to leak after making the switch.
    Has anyone else ever heard or read this? Do you know what has been used in the bike before you acquired it?

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    SMSW's Avatar
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    Re: Synthetic or semi-synthetic?

    Quote Originally Posted by Don B View Post
    the reason for this is the seals and gaskets are more likely to leak after making the switch.
    Has anyone else ever heard or read this?
    I have. Don't know if its true. I'm skeptical (well, cynical, too) until it comes from a proven source.

  9. #9
    Site Supporter Dale_I's Avatar
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    Re: Synthetic or semi-synthetic?

    I'm well versed in the oil market. And, yes and no. There are some laws regarding the use of the terminology. But, they do absolutely no good. They give a source the ability to advertise as synthetic without being fully synthetic. Without getting into Group 4 PAO base stocks and such, the synthetic world is so muddled in garbage you really have a hard time knowing what you're buying without looking into the specifications of it.

    One of the most used tests quoted recently seems to be the ATSM "Fourt Ball Wear Test"... which is for gear lube and not motor oils... which doesn't make it completely irrelevant, but certainly confuses the playing field even more because the parameters don't mimic an engine.

    You can generally tell by cost. A fully synthetic oil will be 3 to 4 times more expensive than a blend. Schaeffer's 9000 line or Amsoil would be examples of full synthetic.

    The reason for the motors/transmissions leaking is because of how pure the synthetic oils are. If you have a failing gasket that has been effectively plugged with sludge that has been preventing a leak... then you add detergents to break down sludge and an oil that doesn't have the byproduct of contaminants that create the sludge... you've created a leak. Realistically, your gasket failed a while ago and the problem has just been lurking, waiting for the perfect moment to really flow. (Sat night on the 3-day Monday off weekend in the middle of nowhere, add whatever weather you dislike the most).

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