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So is synthetic oil a real No-No?

Discussion in 'XJ Technical Chat' started by DrewUth, Mar 24, 2016.

  1. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    I'm getting the same feeling I got when Bill Gates and Steve Jobs agreed to work on cross-platform-compatible operating systems. Hurray for companies that want universal standards!!
     
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  2. XJ550H

    XJ550H Well-Known Member Premium Member

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    I was not rich/privileged had a nice 67 GTO, 68 442 and 69 firebird , I guess it was all in what you spent your money on and how much you wanted to work for the "nice Cars"
     
  3. RECAC

    RECAC New Member

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    Everyone has their own preference concerning the choice of oils. Hopefully, reaching it involved their experiences and those of others. Mine is Amsoil. 76,000 on the XJ. Might be luck or synthetic oil.
     
  4. DrewUth

    DrewUth Active Member

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    Everyone he knew drove ratted out straight-6 cars/wagons or VWs. Kudos to you for having a nice car in HS. I know he worked hard for his Beetles and Thing.
     
  5. Bluestar

    Bluestar New Member

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    Synthetic Mobil 1 motorcycle oil made my starter clutch spin like a bag of marbles, it took about 2 years before it happened. I flushed it out twice using mineral oil and it never happened again. It’s not Mobil fault, it’s the synthetic oil from any manufacture. I had used AMSOIL too with the same spinning results.
     
  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    I would imagine if everything was new on your motorcycle starter clutch, drive clutch, that you may not have any trouble whatsoever using synthetic oil. If your clutch is worn ,you starter clutches got many miles on it things may start slipping. Many people have success with the synthetic many do not. I look at it this way synthetic was not specced for the bike so I do not use it.
     
    Last edited: May 1, 2021
  7. Pizzaman

    Pizzaman Member

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    Is the damage sometimes permanent from using synthetic? Or does just switching back to regular oil fix the issue?
     
  8. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Typically no, because as soon as the clutch starts slipping, youre gonna stop riding..... since it slips so bad. Then you realize why, and drain the oil and put good old Dino juice in and the problem goes away.

    I still just use Yamalube 10w40 in all my XJ’s
     
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  9. XJ550H

    XJ550H Well-Known Member Premium Member

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    Some have had success changing back to conventional oil. May require a little flushing of the starter clutch or a couple of oil changes. I don't know if seafoam would help remove the synthetic oil.
    I don't think it does damage as much as it is as it is slippier formulated to penetrate into the smallest of parts tighter tolerances of the modern motors.
    I find it cost more than conventional oil so I don't understand why somebody would use something that they don't need to but oil being oil that's a personal choice.
     
  10. cgutz

    cgutz Well-Known Member

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    For years I have used
    Shell Rotella T4 Triple Protection Conventional 15W-40 Diesel Engine Oil

    Great stuff, cheap, no issues.
     
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  11. Franz

    Franz Well-Known Member

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  12. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    I am in the process of switching from Castrol Actevo 10W-40 to Rotella T4 15W-40. Never had a problem with the Castrol, it is just that the T4 is cheaper, and I never come close to putting on enough miles to warrant an oil change (I change annually, at least), so it just feels less wasteful.

    Looks like the Rotella T6 is JASO rated if one really wanted to try some synthetic. Probably what I would do if I put on enough miles.
     
  13. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    I do find that the discussions about oil are pretty interesting.

    Seems like there are a lot of religious beliefs out there.

    As @k-moe has said before, standards are standards. If an oil is JASO certified, whatever that means, it should be good.

    Just because you experienced a major failure while a certain oil was in the engine does not mean that the failure was caused by that oil. In other words, correlation is not causation.

    I guess oil is just one of those things that people will always have religious beliefs about, but there is very little hard data to back anything up - other than we do know that modern day friction modifiers are bad for wet clutches.

    So if you put in a synthetic with friction modifiers and your clutch slips, it's not the synthetic oil that is the problem, it is the additive package. And yet, it is very easy for someone to say "I used X synthetic oil and my clutch slipped" - that is a useless statement without stating if you used something JASO rated or not.
     
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  14. tj.

    tj. Active Member

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    If you are looking for data...send for analysis. $20 if I remember correctly.
    https://www.blackstone-labs.com/
     
  15. Dave in Ireland

    Dave in Ireland Well-Known Member

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    In my direct experience it's time and mileage that are more responsible for slipping clutches than anything else.
    Sure, I had a slightly slipping clutch after I filled with synthetic, but that clutch had done 90K hard-fought back-road miles by then.
    A top-end rebuild a year or two later saw me replacing the friction plates (and fitting new OEM springs) as part of that overhaul and I've been using synth oil since then with no slippage.
     
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  16. SQLGuy

    SQLGuy Well-Known Member

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    I have found the Mobil 1 4T 10W40 to be good. I had previously tried Amsoil 20W50 and Mobil 1 V-Twin 20W50, and both of those made the starter clutch slip. The Amsoil wasn't as bad as the Mobil 1. With the Mobil 1 20W50 the starter clutch was useless. Drained and refilled with the Mobil 1 10W40 and it was immediately fine.

    I like synthetic in these bikes, though, because the oil gets very hot compared to water cooled engines and conventional oils will break down pretty quickly at those temperatures.
     
    Last edited: May 4, 2021
  17. cgutz

    cgutz Well-Known Member

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    I have used conventional oil since my XJ550 was new from the showroom. I do oil changes every season or 2k miles, whichever comes first. Approaching 30k miles and no clutch or engine issues.

    I admit I don't do a lot of hard, long distance traveling anymore, especially in really hot weather. I love my car AC too much.
     
  18. XJ550H

    XJ550H Well-Known Member Premium Member

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    I think you are correct on that thought.
    if your bike has a new clutch and starter clutch synthetic should give you no issues.
    if it has old clutches why poke the dragon.
     

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