Forum Discussion

jolooote's avatar
jolooote
Explorer
Nov 14, 2012

Onan 5500 Marquis Gold, OIL?

My Onan 5500 Marquis Gold in my 2006 Class'A' MoHOme has almost 500 hours on it. I'm still using the 15W-40 grade of oil that was originally recommended in the manual. Should I start using a different weight/grade of oil? Maybe also switch to full Synthetic?
Class A

16 Replies

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  • SRT's avatar
    SRT
    Explorer
    Nov 15, 2012
    Synthetic 15W-40 in our 5.5 Onan. Don't recall the hours on the meter.
  • bob_b1's avatar
    bob_b1
    Explorer
    Nov 14, 2012
    I just hit 1000 hours with my 20yr old Onan. I still use the 15W40 because that is also what my Cummins diesel takes. The generator runs well. Why mess with success?
  • ArchHoagland's avatar
    ArchHoagland
    Explorer
    Nov 14, 2012
    Let sleeping dogs lie.

    Don't change horses midstream.

    If it ain't broke, fix it till it is.

    I'd stay with what you have been doing.
  • pkunk's avatar
    pkunk
    Explorer
    Nov 14, 2012
    1450+ hrs on my 5500 w/ 15W40 dino, change once a year and exercise once a month or so. Sometimes runs for 6-7 hrs in hot weather when we need air.
  • fredbon's avatar
    fredbon
    Explorer
    Nov 14, 2012
    I made a switch a few years back, unit started smoking on start and using oil. Went back to Onan's oil, problems solved.

    Stick with Onan Store, you will get the right parts without running around.

    fred
  • bsinmich's avatar
    bsinmich
    Explorer
    Nov 14, 2012
    Does the book say to switch to a different grade after so any hours? I would stick with what works. I put synthetic in my Generac and have had no problem, but Generac doesn't recommend the 15W40 either.

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