2 cycle oil in diesel fuel

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  • July 13, 2011 3:40 PM
    Message # 653873
    Deleted user
    I had a trucker friend that also is a boater tell me he always adds 2 cycle motor oil to his diesel fuel to smooth the engine out in his big rig. Says he swears by it. I "googled" the topic & found varying opinions as to the effectiveness of the practice. The concensus was that it would be good for the injector pump and injectors, would burn away cleanly and even if it didn't offer any real help to the engiine running smoother, it certainly wouldn't hurt it.

    Soooooo...I tried it. I added some 2 cycle oil to the fuel with my next fill up. I added enough oil to yeild a 128:1 mix (one ounce of oil to each gallon of fuel). I also added my regular mix of fuel stabilizer. After starting the engine, I sat back and just watched the tiller handle for a few minutes. It was amazing! The tiller handle went from strongly vibrating to almost no detectable vibration at all. As we ran the engine out at higher RPM next time out, we noticed much smoother and quieter operation.

    I'm sold! Anyone else ever had any experience with this?
  • July 24, 2011 9:18 PM
    Reply # 662195 on 653873
    Deleted user
    Apparently no one has any idea.  Wish someone did.  Can't see it would do any harm in such a small amount - good lubrication, especially with the new low sulfur, poorly lubricating diesel, although a very high concentration might cause coking of the cylinder heads and valves.  But why 2-stroke oil?  More combustible so lower coking tendancy?
    Last modified: July 24, 2011 9:19 PM | Deleted user
  • July 31, 2011 7:38 PM
    Reply # 666840 on 653873
    Deleted user


    It seems that the older I get, the more I rely on empirical evidence. The "experts" many times have an agenda or stated more bluntly, don't know what they are talking about. I did some research based on your post and came to the conclusion that once again information from someone who has done it has it all over someone who has a theory. Today I added 19 oz. of 2 cycle oil to my starboard tank which contains 19 gallons of diesel fuel. I ran the engine at 1400 RPM which is where I experience maximum vibration. Bottom line is that my original Volvo MD 11, affectionately known as "Old Thumper" liked the mix very much. I noticed the following within about 15 minutes or so.

    Noticeable reduction in vibration.

    Noticeable reduction in engine noise.

    No knocking or detonation when accellerating to higher RPM as previously experienced.

    Oil smoke although minor to begin with, disappeared.

    In short, instead of sounding like a collection of parts trying to fly in different directions, "Old Thumper" sounds like a smoothly running diesel engine. (At least for a two cylinder.)

    I ran the engine under load and stopped and re-started it several times. No hard starting or tendency to run-on when shutting down.

    I may have to come up with a new name for "Old Thumper".

    Thanks for passing this on. I think I just got a top overhaul for $ 4.00.


  • August 03, 2011 5:56 PM
    Reply # 669129 on 653873
    Deleted user
    Glad to hear it Werner! That confirms that our experience wasn't just a fluke. Hopefully, this little trick will add some years to our trusty engine's life!
  • August 03, 2011 8:16 PM
    Reply # 669202 on 653873
    Deleted user

    I've never tried it, but I'm going to now!  The reason for using 2-stroke oil would be that it is designed to be burned, whereas other lubricant oils (like a 10/40, for example) are not, and would smoke alot more (probably due to the amount of detergents in the chemical package).  A bit of background... I've been a mechanic for 20 years. 


  • September 15, 2011 6:42 PM
    Reply # 700785 on 653873
    Deleted user
    I often add a quart of automatic transmission fluid to a 20 gallon tank of diesel on our two tractors.  Gives a little extra lubricating ability to low sulfur diesel, and burns as well as diesel.
  • October 06, 2011 6:15 PM
    Reply # 716918 on 700785
    Ralph Weiland wrote:I often add a quart of automatic transmission fluid to a 20 gallon tank of diesel on our two tractors.  Gives a little extra lubricating ability to low sulfur diesel, and burns as well as diesel.

    BoatUS had an interesting article in Seaworthy this month. I thought I'd pass it along...

  • October 16, 2011 4:34 AM
    Reply # 723890 on 653873
    It works!   I was skeptical but I tried it.  It really did work. 

    For years, I attributed the vibration in the tiller under power to imperfect shaft alignment.  After trying the oil in the fuel trick, 3/4 of that vibration disappeared instantly.  I'm sold.

    Wal Mart sells a gallon of 2-cycle oil for $12.50.  That makes it affordable.

    Thanks for the tip.

  • October 19, 2011 5:57 AM
    Reply # 726764 on 653873
    I shared this thread with a friend who has a Perkins 4.108 in a CSY 37. He found and passed along a similar link regarding the use of Marvel Mystery Oil for the same purpose...

    Can I use Marvel Mystery Oil® with diesel fuel and if so, how much do I use?  Yes, you can use MMO in diesel fuel as well as gasoline. Use the same amounts as the gasoline treatment recommendations-4ozs of MMO for every 10 gallons of fuel. However, MMO does not comply with federal low sulfur content requirements for use in model year 2007 and newer diesel motor vehicles.

  • May 22, 2012 7:23 PM
    Reply # 928014 on 653873
    Deleted user
    Six months now using the 2-cycle oil in the yanmar 3GM30 on Sea Gyspy. The engine continues to run better & better with every use. I'll never run a marine diesel again without the extra lubrication!
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