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Thread: Mixing Oil Viscosity

  1. #1
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    Mixing Oil Viscosity

    Changed oil in the beast today and realized I screwed up and grabbed 2 gallons of 5-40 and 2 gallons of 15-40. So I now have 8 quarts 5-40 and 7 quarts 15-40 in the engine.

    I'm running Rotella T6 synthetic...

    Preliminary research on the interwebs make me feel this will be fine but thought I'd throw it out to the motor heads here as well for an opinion..

    It's almost a hundred dollars worth of oil so I really hope not to have to drain and replace.

  2. #2
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    I wouldn't worry about it.
    The only way of discovering the limits of the possible is to venture a little way past them into the impossible - Arthur C. Clarke

  3. #3
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    I wouldn't think a one time mix of viscosity if it's all Rotella T6 would hurt anything...Here's an opinion from Mr. Google...But then I've never used synthetic, so my theory may not be valid......Ben
    The future is forged on the anvil of history...The interpreter of history wields the hammer... - Unknown author...

  4. #4
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    Found this :

    Here is the rest of the story from an email I have from Shell:

    All of our Shell Rotella multi-grade viscosity products are
    completely compatible with one another in any ratio. A 50/50 blend of Shell Rotella T Triple Protection Oil SAE 15W-40 with our Shell Rotella T6 Synthetic Oil SAE 5W-40 would be perfectly acceptable. You could then switch to Shell Rotella T5 Synthetic Blend Oil SAE 10W-30 whenever you desire. Thank you for your interest in Shell Lubricants! Regards, Edward A. Calcote Staff Chemist Shell Lubricants US Technical Information Center
    The only way of discovering the limits of the possible is to venture a little way past them into the impossible - Arthur C. Clarke

  5. #5
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    I'm reminded now of what I did in my career as a mechanic...When I changed the oil in vehicles for other people I let the drippings from the oil cans drain into empty antifreeze bottles...I liked to change my own oil at around 1,000 miles (overkill I know) and the drippings were what I used along with a new filter...The oil was various brands and viscosity...The shop helper saw what I was doing and said he'd change my oil for me if he could have my drained oil and the old filter...He then changed his own oil and filter, using what he took out of mine since we had the same engines...His theory was that if something was wrong with my oil there would have to be something wrong with my engine, and there was nothing wrong with my engine...

    Neither one of us ever had an engine problem......Ben
    The future is forged on the anvil of history...The interpreter of history wields the hammer... - Unknown author...

  6. #6
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    189000 miles and going strong...

    On a side note. Just had 5 A10's fly over mi casa heading for Luke AFB.. Bad ass!!!

    Must be an exercise going on because i saw 3 Black Hawks lift off from Scottsdale Airport this afternoon... Good stuff!

  7. #7
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    There is no science in this--and I have none to offer.

    That said--I have always avoided mixing brands of oil out of an abundance of caution that the additives could react with each other. Since I have not violated that rule I have no "proof" to offer
    "A pessimist sees the difficulty in every opportunity, an optimist sees the opportunity in every difficulty” ---Sir Winston Churchill
    "Political extremism involves two prime ingredients: an excessively simple diagnosis of the world's ills, and a conviction that there are identifiable villains back of it all." ---John W. Gardner
    “You can’t go back and change the beginning, but you can start where you are and change the ending.” ---C. S. Lewis

  8. #8
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    Same brand, just different weights.

  9. #9
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    If you are still concerned, contact Shell: generalpublicenquiries-us@shell.com
    The only way of discovering the limits of the possible is to venture a little way past them into the impossible - Arthur C. Clarke

  10. #10
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    Not really concerned any more. I talked to my buddy/mechanic and he said it's nothing to worry about.

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