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Will synthetic engine oil cause a high mileage engine to leak?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Piranha300, Jul 25, 2001.

  1. Piranha300

    Piranha300 Registered Member

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    ???
     
  2. muddin4fun

    muddin4fun 3/4 ton status

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    I had a pickup with high miles on the motor. I put a semi synthetic in and it ran like crap! I couldn't figure it out. I changed the oil back to a regular oil and it ran fine. I don't know why it makes a difference, but it did in that truck.

    I've got a mind like a . . . a . . . what's that thing called?

    <a target="_blank" href=http://www.geocities.com/muddin4fun79blazer/>http://www.geocities.com/muddin4fun79blazer/</a>
     
  3. rampage

    rampage 1/2 ton status

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    YES !!
     
  4. Pure Insanity

    Pure Insanity 1/2 ton status

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    I have personally seen slick 50 wipe out a perfectly good motor. It was a higher milage LUV truck that ran great......add slick 50 and all the seals started leaking so badly after a few days the truck could not be driven to the shop, cuz it wouldnt hold oil long enuff to make the trip.

    Out of 100,000 sperm, YOU were the fastest?? [​IMG]
     
  5. yeild2me

    yeild2me 1/2 ton status

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    i bought my truck with 90000 miles on it with the rear main leaking and it smoked on startup everymorning. i switched to synthetic blend, then a few thousand miles later went to totally synthetic, and guess what???? the main STOPPED leaking, and it STOPPED burning oil!!!!! i dont know how this occured, but i swear it did. my truck now has 160000 on it, and it still is great. i use castrol GTX and usually change around x-mas every year.

    c:\program files\ulead systems\ulead photo explorer 6.0\cache\img00010.jpg
     
  6. talldogg

    talldogg 1/2 ton status

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    Here's some more answers to your question...
    <a target="_blank" href=http://www.impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&amp;f=33&amp;t=000244>http://www.impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&amp;f=33&amp;t=000244</a>

    It's not what you buy, it's what you build!
     
  7. 84_Chevy_K10

    84_Chevy_K10 Banned

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    If your seals are marginal, yes, it will leak, because the molecules are smaller and it finds leaks. I wouldn't do it on a high mileage motor either.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  8. newyorkin

    newyorkin 1 ton status

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    I used to think synthetic was retahded, but then I actually read up on it. I've never heard of it causing any leaks, in fact, I'd think it would condition the seals better against leaks, but I guess other guys here have seen it. Strictly my opinion, but if synth is gonna make it leak, it was probably gonna leak anyway, or, like someone here or the impala site said, the leak was being masked by the burnt sludge...
    Quaker State has a synthetic blend for Higher Mileage engines that's specifically designed to condition worn or old seals. You might want to try running 6 or 7k on that before doing the full switchover.
    Are you leaking now?
    Why not try a few motor flushes before changing over?
    See what comes out with a flush...

    I just switched over to completely synthetic blend, and so far, so good (was running half conventional/half compatible synth before). Seems to run a little nicer, but that could be the new oil pump I did at the same time. So far, no leaks and pressure stays more consistent longer! But my engine doesn't look like it had/has any sludge in it.
    I also just switched my wife's 130k 2.8 over to synthetic, and it does seem to run better, and got phenomenal emissions numbers. It's leaked oil since we got it, though, so I can tell ya synthetic didn't do it! I used 1 quart of higher Mileage blend and Mobil 1 to fill up.

    I've noticed some folks make the mistake of changing thier oil grade when switching over (only twice actually), so maybe that's why some p[eople have had a problem going to synth? I'm still too new to running on it to say, but I've never really seen any problems on motors I know of running it.

    The molecules in synthetic are actually consistent size, while petroleum product molecules are random sizes due to being a refined natural product (sludge is caused by the smaller molecules being burnt and larger molecules carrying them). What makes the difference to the engine is the viscosity index.
    Here's a great ref for that (almost exactly what I just said in better detail, maybe making better sense than my tired mind):
    k5.8m.com
    **K5 - What more is there to life?**
     
  9. 1990K5

    1990K5 1/2 ton status

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    YES-- it will definately cause leaks on a higher milage motor
     
  10. Blazer79

    Blazer79 1/2 ton status

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    Interesting link, Talldog. This is the most interesting part:
    <a target="_blank" href=http://www.geocities.com/chrislonghurst/engineoil_bible.html>http://www.geocities.com/chrislonghurst/engineoil_bible.html</a>. I really recommend you read it, especially if you're a newbie...uhm, pavement pounder. [​IMG]

    <font color=purple>//////
    <a target="_blank" href=http://blazer79.freeyellow.com>blazer79.freeyellow.com</a></font color=purple><font color=black>
    Soon a 454 K5!!</font color=black>
    [​IMG]
     

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