Can anyone decipher an oil sample??

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Elroythekid, Oct 14, 2011.

  1. Elroythekid

    Elroythekid Road Train Member

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    OK, so... I had samples pulled from the 378 Im looking at and would like to have somebody have a look at it for me, is there anybody who REALLY knows what these things are saying?
    It was a long interval on this sample and it was flagged for high oxidation and elevated iron, it went 62,000 kms from the last change, the viscosity is still up at 18.5 V100. Cat and Peterbilt Machanics are saying its ok, wait for blow by test on the dyno (monday am) and that will tell you if there is any damage, with the viscosity still high its just saying the oil was tired change it?
    Thanks
     
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  3. Heavyd

    Heavyd Road Train Member

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    The oil viscosity is only one ingredient of good oil. There are numerous additives that get used up over time. The long interval will show higher levels of contaminants because they are comparing to normal benchmark levels based on 40K intervals I would imagine. We like to see at least two consecutive oil samples with consistent contamination problems before we look into it further.
     
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  4. Roadking58

    Roadking58 Bobtail Member

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  5. Elroythekid

    Elroythekid Road Train Member

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    Problem is I have to pull the trigger on this or not. Monday's dyno test is going to include blow-by, what is an acceptable level for a C15 with 700000 kms on it? At what point is it run, don't walk?
     
  6. Heavyd

    Heavyd Road Train Member

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    Lots of trucks out there, don't ever be pushed into buying something because "time will run out". There is always another truck.
     
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  7. Shade Tree

    Shade Tree Light Load Member

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    The question to really ask is if you are having a higher than normal oil usage. Blowby is normal and if high, so will your oil consumption be higher than past experienced. Blowby is measured with a water manometer or should be, and there is a specified range, but a higher than normal reading is usually accompanied with high oil usage. There are other internal engine problems that can cause a high blowby issue if you aren't experiencing a high oil consumption problem. A good CAT mechanic should know how to differentiate the other issues. I believe CAT was stating oil consumption is relational to gallons of fuel used, not oil usage per miles driven. If you haven't had an increase in oil consumption then use it as a benchmark as previously suggested. When were the rod bearings changed? If it has over 500K on the bearings then I would suggest getting a bearing rollin done (soon), and you may find that some of the metal content, is part of normal bearing wear because of the metal content in CAT bearings.
     
  8. Gambi80

    Gambi80 Medium Load Member

    x2...! Though, if it's a cherry day-cab, they are not easy to come by.

    On the oil sample, I have been led astray before by someone inputing the wrong information into the 'machine' and it produced a false bad sample...had me sharting bricks for a while untill I had it sampled again and it came out fine.
     
  9. Elroythekid

    Elroythekid Road Train Member

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    The truck only has 450k miles on it and has had no major work done yet, im just wondering how much damage has been done by this owner leaving his changes to 31k miles? He is second owner and has had it for 3 years.
    The sample history look like he did the first few changes at earlier intervals and they looked good, but the last 2 changes were much longer, hence the second to last sample flagged for elevated oxidation, and the sample I had pulled red flagged for high oxidation and high iron, which is caused, (or so the lab guy told me) by the high oxidation.
    Tomorrow am is dyno and blow by test, what is acceptable for blow by?
     
  10. king Q

    king Q Road Train Member

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    62 000Km = 38 533,25 miles.
     
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