what causes oil to turn black in like 4 days???

Discussion in 'Mechanic and Repair' started by milo, Mar 2, 2007.

  1. milo

    milo LawnSite Bronze Member
    Messages: 1,308

    anyone know why in my one mower why after changing the oil it turns black like in 4 days of using it?? i change the filter to. i changed it like 3 times in 3 weeks and still goes right to black.. any clue???
  2. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    First thing I would do is check the owner's manual and make sure you're using the correct grade and type of oil, just to be certain.

    Beyond that there exist two things I know of, one is a gunk buildup generally caused by letting it go too long between oil changes. If the buildup is severe, it can take numerous oil and filter changes before all the sludge is dissolved.

    You might try doing a motor flush, I would warm up the engine and shut it off, add 1/5th of the engine's oil capacity in kerosene, start and run it for 8 minutes on idle (do NOT rev) and shut it off again, then drain and change oil and filter immediately and see if that helps.
    - A 5 quart capacity engine takes 1 quart of kerosene (such as a car or truck).
    - A 2 quart cap. engine would take 64/5 = 12 ounces of kerosene, about 3/4 of a pint, a bit less than 1/2 a quart of keros.
    Yes, this helps considerably in dissolving gunk and sludge, but you should only do this in severe cases because it's not the best engine treatment.
    Again, warm it up, shut it off, add a little keros, start it and run it on idle ONLY for 8 minutes, shut it back down and change oil and filter immediately.

    Worn rings can cause it as well, what happens is exhaust gases get past the rings and into the oil, turning it black. In this case nothing short of a rebuild will take care of it, thou I'd recommend an engine swap, it's up to you what to decide and normally you'd notice a lack of power or compression as well, but the motor flush can help narrow it down for you.

    Good luck
  3. spinrider2000

    spinrider2000 LawnSite Member
    Messages: 75

    Milo, being in automotive for many years, there are some reasons that the oil darkening may not indicate a problem. The newer oils are designed to darken. As they work, they darken, which really means the oil is doing what it is designed to do. Of course there are engine conditions that can contaminate oils. Do not let the color be the only (single) indicator of oil condition. Lawn engines & auto engines do not operate under the same conditions, but just my 2cents.
  4. johng

    johng LawnSite Member
    Messages: 52

    My first guess would be incomplete combustion or worn or stuck rings.
    The first thing could be caused by the second or a carb that is running too rich or a lack of compression. I always check compression next thing while I'm looking at the plugs.
  5. The Captain

    The Captain LawnSite Senior Member
    Messages: 607

    I have to side with spinrder2000 on this. Several years ago I worked at a service station, you older guys know what I mean by service station. My boss bought a brand new Chevy and spared no expense caring for it (it was his station and supplies). We saw that when the oil was changed (always with a new filter) the oil turned black in a day or two with only small town driving. We changed it every day for a week with the same results. Why???? The company oil reps. that used our station said the premium oil would/should do that by design. ?????? No reason why.
  6. Drew Gemma

    Drew Gemma LawnSite Bronze Member
    Messages: 1,508

    if it ain't burning oil or leaking let it be. More than likly it is the metal from the engine leaving mineral depositis in the oil common happens to all.
  7. LCPullman

    LCPullman LawnSite Senior Member
    Messages: 589

    On my diesel engines, the oil turns black very quickly, by products of diesel combustion get into the oil and turn it black quickly.
    In my mower (gas) engines, the higher the temperatures the oil is exposed to, the faster it darkens. During spring, I can run a full 100 hours with minimal darkening. During summer its quite dark within 50 hours.

    Another point, do you drain a warm engine? If you drain the oil when its cold and thick, more old oil is left in there and its amazing how much old oil darkens new oil.

    I'm assuming you talking about a gasoline engine, but if your talking diesel, make sure you use oil designed for diesels.
  8. spinrider2000

    spinrider2000 LawnSite Member
    Messages: 75

    It seams from the past that the better the oil additive package, the more contaminents would be held in suspension. Oil color is definitely not an indicator. Look at Mobil 1 extended after 10k miles. Tar black and still good. A little off the mower subject but.....watch other conditions for the real story.
  9. carcrz

    carcrz LawnSite Silver Member
    Messages: 2,085

    What kind of motor is it? If it's a Diesel, that's normal. My Dodge is almost black by the time I get out of the driveway from the soot in it.
  10. AintNoFun

    AintNoFun LawnSite Bronze Member
    Messages: 1,807

    yea thats no lie about oil turning dark in diesels, im pretty sure you could run the motor for 10 seconds and it would be black...

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