C15 Synthetic or Not?

Discussion in 'Ask An Owner Operator' started by Swift09, Mar 27, 2020.

  1. Swift09

    Swift09 Bobtail Member

    Jul 4, 2019
    I bought my truck with a rebuilt mbn, has about 130k on the rebuild.

    I added a gallon of synthetic this week and it's leaking at the front casing.

    I want to do an oil change. Should I stick to regular? Or try synthetic?

    Recommendations on brands? Thank you for the help
  2. Judge

    Judge Road Train Member

    Mar 19, 2014
    Newport, Ar
    I would stick with rotella 15W-40.
    I always heard if there’s a place to leak synthetic will find it.
  3. Cat sdp

    Cat sdp . .

    Apr 8, 2012
    Orion's Belt
    I’ve used T6 forever in a C15...... fix the front cover.
    It was probably leaking before anyways.
    Orange713 and mtoo Thank this.
  4. First where's it leaking on the front cover ? Crank seal probably wasn't part of over haul if inframe. Probably ready to leak from age. Leaking from behind fan hub mount the one stud (top driverside) common issue of leaking. Two ways to fix. Cheap way,pull stud clean stud and hole use silicon adhesive (not to much) put on stud threads and install. Let it cure and it will stop leak. Or expensive way remove front cover and replace front cover and plate gaskets.
  5. Midnightrider909

    Midnightrider909 Road Train Member

    Oct 26, 2016
    Always use synthetic if you own it.
  6. I switched to synthetic blend oil (shaffers) and no leaks.
  7. PE_T

    PE_T Road Train Member

    Try to locate your “engine manual” online, which is not the same as your truck manual. There should be a section about engine oil types for your engine. I’d stick with what they recommend.

    I personally use synthetic blend for my DD15 engine (2013 model). Full synthetic is very expensive.
  8. moonshine powered

    moonshine powered Bobtail Member

    Oct 28, 2014
    Exactly this!
    I used to run T6 in everything I owned, when I purchased my truck eith a 2WS Cat there wasn't a drop of oil anywhere. Even on the 2000 mile drive home nothing. Swapped it over to T6, it was like I drilled holes all over the thing. I couldn't keep the oil in it. Went to Mobil delvac 1300... No leaks.
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