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Engine Oil Fuel Dilution Above Cummins Guideline of 5%


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2004 Monaco Dynasty Regal 42 with 72,000 miles. Well maintained.
I just had the engine oil tested and the fuel dilution came back at 8.5%. The Cummins engine guide shows a 5% amount. The lab test report does not show any significant level of engine wear contamination. There is no gain occurring in the oil level when the RV is driven so I suspect that the problem is from idling too long and stop and go traffic. 
I need to make a 300 mile trip on I64 through southern West Virginia and Virginia before I can get the oil changed. Lot of low-level mountains.
I can go 100 miles out of my way to get the oil changed before I make the trip home or I can drive home and get the oil changed after I get home.
If anyone has diesel engine experience in this area please let me know what your opinion is?
Thank you in advance for your thoughts.

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Operating a diesel with that much dilution will almost ALWAYS be fatal. I would not run that engine without changing the oil AND eliminating the source of the diesel fuel. That 5% limit was established for a reason and you are almost TWICE that number.

You sound like you're going to run it anyway so take a moment to think about the cost and heart ache that will result. You may make it the 100 miles but every mile driven is shortening the life of that engine. It may not sieze today, but what about tomorrow?

Good luck

 

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To further elaborate, the oil capacity on my engine is 12 gallons. With 8.5% dilution that would mean approximately 1 gallon of the total is diesel fuel.

Diesel fuel use to have some lubricating properties but since the low sulphur requirement, not so much.

I would also disagree with the suspected cause of the dilution. I don't think it's even reasonably possible to idle a diesel long enough to get that level of dilution.  At least I've never seen or heard of it happening in the 26 years I worked in the field.

By the time you see a drop in oil pressure the damage is already done, you're just waiting for the bang.

Oil changes are CHEAP compared to the cost of a new engine.

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Sorry Lee. Change the oil before you drive it and nail down the cause immediately. 

It may be something else and dilute the oil even more before you get to your destination.   It very likely could do major damage.  

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Could the number be off?  Not enough time for a re-test, but . . . . Maybe send in another kit for confirmation then have the oil changed.  Send in a kit with the fresh oil for a baseline and another kit x,000 miles later.  See if there's a trend.

Just MHO,

- bob

 

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My thanks to all for the information.
I was told by a Cummins factory service center to go ahead and drive the 100 miles to their location for the oil change.
I am not comfortable doing so.
I have submitted an email direct request to Cummins. The Cummins website states that they will respond in 24 hours.
I will also try to call Cummins direct. The Cummins website provides the number for the call.
I do agree that this is a very serious matter.
I will post their answer.

Thanks again for all of the help.

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I think regardless of what cummins says I would dump the oil and add in new before i drove it. If you couldn't get the filters changed I would think skipping them would be OK till you got home. If your not capable of doing this you could get the oil and a couple containers to put the used oil in and have a mobile repair guy do it for you. 

I would also pull another sample of the used oil just to verify the results and test the new oil once I got home. 

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On 2/9/2022 at 7:57 PM, Lee Smith said:

2004 Monaco Dynasty Regal 42 with 72,000 miles. Well maintained.
I just had the engine oil tested and the fuel dilution came back at 8.5%. The Cummins engine guide shows a 5% amount. The lab test report does not show any significant level of engine wear contamination. There is no gain occurring in the oil level when the RV is driven so I suspect that the problem is from idling too long and stop and go traffic. 
I need to make a 300 mile trip on I64 through southern West Virginia and Virginia before I can get the oil changed. Lot of low-level mountains.
I can go 100 miles out of my way to get the oil changed before I make the trip home or I can drive home and get the oil changed after I get home.
If anyone has diesel engine experience in this area please let me know what your opinion is?
Thank you in advance for your thoughts.

Lee,

Was there a reason you had the oil tested at this time?  Were you experiencing any abnormalities?  Or was it just PM?

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