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Asking for a friend, seriously. Will DEF fully separate from diesel fuel?

Shimmy1 · 2026-02-12 23:00

As the title says, if you pump 200 gallons of diesel fuel into a tank that had about 15 gallons of DEF left in it, is the whole shitteree burnpile fuel? Does the urea stay mixed with the fuel, and just the water separate out? It's a storage tank, not on a piece of equipment, and nothing has been pumped out, luckily.

Replies32
  1. #1MarshallPowerGen2026-02-13 00:40

    That's almost 10% contamination of water/DEF that will destroy pumps and injectors if used. Can let it settle and pump the water out of the bottom, but the cost to polish that fuel and the amount of hydroscopic filters you'd go through to clean it still wouldn't be worth the risk to run it in any equipment. Pump it out as trash and move on.

  2. #2Coaldust2026-02-13 01:43

    200 gallons of ULSD. That’s a cool G-note in fuel. I think you could salvage it. You are in NoDak. Let that stuff freeze at 11F and pump the fuel off. The urea can’t mix with the fuel.

  3. #3HarleyHappy2026-02-13 09:13

    Give it away. I would consider making sure it’s settled and trying to maybe pump out 3/4 or maybe more. Making sure you use a clear hose and visually watch it and maybe pumping into another tank or drums. Still a pretty expensive gamble, one way or another.

  4. #4heymccall2026-02-13 09:40

    https://www.quora.com/How-do-you-remove-DEF-from-diesel-fuel

  5. #5Simon C2026-02-13 10:28

    One guy I met that was experiencing loss of fuel at night would pump something like that into a regular tidy tank and leave it on the end of driveway for them to come and pump off during the night. Like he said they wont be back. Maybe it can be pumped off properly, its worth about $1000 in Canada, not even the price of one injector on some machines if anything makes it through. I would take a small sample of clean fuel and contaminate it with DEF, then pump off the top with a syphon hose and have it tested and you would know for sure for about $30 or less. Simon C

  6. #6Truck Shop2026-02-13 11:36

    For what it's worth. My old company had a disgruntled employee about 7/8 years ago that sabotaged two tractors with about a 1 gallon-1 quart in each tank, 120 gallon tanks that were parked with full tanks. Cost to replace fuel systems on both ran roughly $13,000 plus each. Injectors, pumps, fuel coalescers, fuel lines, tanks were steamed. * The 200 gallons is chicken feed.

  7. #7Coaldust2026-02-13 11:46

    It makes good heating oil.

  8. #8stinky642026-02-13 15:50

    Waste oil burner after separated?

  9. #9skyking12026-02-13 16:19

    Yeah that's the perfect solution. Burn it in a heater.

  10. #10Coaldust2026-02-13 16:44

    Trans mix, flush, pump out, mis-fills, that stuff goes for $.50 or a $1 per gallon. Then, gets mixed with clean #1 in 10K or 30k gallon tanks until it meets spec and sold as heating oil. Or, depending on the market, storage and season, it gets mixed with used engine oil and sold as RFO/LDO to the asphalt companies to heat their plants. Nothing gets wasted and the circle of life is complete.

  11. #11Truck Shop2026-02-13 18:07

    Refrigeration compressor oil is a absolute no in a waste oil burner.

  12. #12chidog2026-02-13 19:37

    Ruining a fuel system on the newer stuff, what about the older engines? Isn't DEF similar to urine? So some pee can cause huge problems, even if separated? And then what about addition of oil, after draining off the DEF?

  13. #13Truck Shop2026-02-13 20:44

    DEF is refined Solution 32 Urea used in Ag for fertilizer. It crystalizes forming corrosive deposits clogging filters that can break loose continuing through fuel systems.

  14. #14Truck Shop2026-02-13 20:56

    Most waste oil burners will burn synthetics, used engine oils, some hydraulic oils, gear lube oils. But clean oil doesn't burn it requires fuel deposits to make it combustible. Diesel engine oil that is run on extended services such as 30,000 mile interval will be too thick and soot laden. Any time gear oil, hydraulic oil or thick diesel engine oil is used, to get a burn quality so the CAD CELL can see a proper bright yellow flame off road diesel should be added. Figure for every 100 gallons of waste oil add 25 gallons of off road. My rule of thumb for Black Gold & Energy Logic waste oil burners. I've been dealing with waste oil burners for 25 years.

  15. #15cfherrman2026-02-14 14:36

    Sell it to an oil company to put down an oil well as a treatment

  16. #16Coaldust2026-02-14 15:10

    Great way to dispose of dirty water. I’m surprised how process water flys under the radar up here. The out-of-state special interest groups leave it alone.

  17. #17cfherrman2026-02-14 17:35

    I have around 70 gal at my house to find a home for, I'm not running it in anything, too expensive to fix.

  18. #18DDoug2026-02-14 19:28

    Our DEP is very strict, yet they approved using abandoned mine acid run off water to be used for fracking ..... I guess it's a win-win.

  19. #19masterwelder2026-02-15 09:25

    Any questionable diesel I have gets used in the Steam Jenny.

  20. #20IceHole2026-02-15 10:16

    I've never heard of flush oil getting mixed into fuel. We don't do that for sure.

  21. #21Shimmy12026-02-15 13:19

    Not that you'll admit to, lol

  22. #22Coaldust2026-02-15 16:05

    One particular company gathers it all up, hauls it to a tank farm in Palmer and mixes it up to the proper recipe, BTU content and viscosity.

  23. #23Coaldust2026-02-15 16:07

    Better than Billy-Bob hauling it to Forest Service land and dumping it. Featured Projects | Ahtna, Inc. www.ahtna.com

  24. #24IceHole2026-02-15 23:46

    No, gets used in used oil heaters.

  25. #25IceHole2026-02-15 23:50

    Only 1 Outfit in Palmer with tanks.

  26. #26sfrs42026-02-16 08:51

    Was going to the exact same thing, we had a customer who's quarry was having 100's ltrs a week of red diesel stolen, one week, someone wasn't paying attention while fuelling and checking fluids on an ADT and put 20ltrs of def in the diesel tank, luckily realised almost immediately and before starting the machine, so drained the tank and was going to safely dispose of it... . That's when someone came up with the idea of a small "road diesel" tank near the car park, for company vehicles, little easy to break padlock, camera pointing at the big off road tank not this one, etc, few days later the lot was taken. For weeks afterwards there were reports of contaminated fuel in local garages, but it was always from ford transits owners with Irish accents that had an issues, no one else had a problem. I don't think I've laughed so much before or since.

  27. #27CM19952026-02-17 19:12

    Times so tight up there you're willing to take a risk on 200 gals of contaminated diesel? We don't have the diesel/fuel oil heaters down here so no idea if it can be burned in there or not however there is no way I'm running that in any diesel engine I own.

  28. #28Shimmy12026-02-17 20:48

    It's not mine, I just offered to throw it out for the world to give their opinions. I, personally, not a chance. But, I use probably over half that much every year starting tree piles on fire, so now I'd have a reasonable excuse. The main problem in this situation is it was a wife that did it, she feels absolutely horrible about it, and he was hoping to potentially salvage the fuel so she wouldn't feel so bad. I also posted this on the farmer forum, and got about the same response. Pretty much 50/50, the guys that say throw it are vehement about it, the other half varies from they'd probably use it to they've had many instances in the past where they did use it with no trouble.

  29. #29cfherrman2026-02-17 20:52

    Just tell the wife that we will use it somewhere else, won't get wasted

  30. #30Shimmy12026-02-17 20:54

    I told him I'd take it, but he's determined to use it.

  31. #31cuttin edge2026-02-17 20:57

    When our d4 was new. Operator, older gentleman put def in the hydraulic tank. Lovely shade of pink it turned. Can't remember how it was discovered but it was caught before it ran

  32. #32Mr. Wrench2026-02-18 09:08

    Just wondering what farmers forum you where referring to.