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View Full Version : what causes oil to turn black in like 4 days???


milo
03-02-2007, 03:08 PM
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???

topsites
03-02-2007, 03:22 PM
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.
Examples:
- 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

spinrider2000
03-02-2007, 04:15 PM
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.

johng
03-02-2007, 04:33 PM
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.

The Captain
03-02-2007, 06:05 PM
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.

Drew Gemma
03-02-2007, 06:10 PM
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.

LCPullman
03-02-2007, 08:57 PM
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.

spinrider2000
03-03-2007, 12:00 AM
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.

carcrz
03-03-2007, 12:07 AM
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.

AintNoFun
03-03-2007, 12:49 AM
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...

DiyDave
03-03-2007, 08:33 AM
Change to Amsoil synthetic and test the oil-this will tell whether the oil is actually wearing out. Another possibility I didn't see mentioned is running too hot. Check for clogged cooling fins/sheared fins on fan, lean/rich mixture.

battags
03-03-2007, 11:52 AM
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.


Ditto on that note. As others have mentioned, it my not necessarily inticate a problem to the engine itself. If the oil level stays constant and it's not burning oil when running you should be fine. Make sure your oil doesn't smell like gas, though.

When I do oil changes I drain the oil into an old metal paint pan and put two huge magnets on the bottom. I then drained the oil into jugs for recycling and check the pan for any metal shavings that may have come from the engine. Just an extra check to see how things are going inside between oil changes.


brian

khouse
03-03-2007, 01:49 PM
If it's air cooled you might pull the blower housing and see if the cooling fins are clean. Overheating can cause premature oil failure. Just another thing to check out.

milo
03-03-2007, 03:03 PM
its a 25hp kohler. runs fine, gas. i know oil turns dark doing its job of holding the dirt but this engines oil just gets black in like 4 hours of use. it runs fine and dont burn or leak oil. i just didnt know if there was a reason this one mower does this and my other 25hp kohlers dont. i run castrol oil. 10w30 im guessing it is just old slime build up n there.
well when i start cutting this season i am going to change the oil after every 5 hours like 10 times and see if that helps it.

neighborstree
03-04-2007, 03:27 PM
change the oil when it HOTT. that way you will get the gunk and buildup out of it. it could be blowby. if your rings are worn or whereing you will get carbon deposits in the oil, causing , black oil

tomo
03-04-2007, 04:55 PM
hello, air cooled kohlers 25 hp carby

run a very small sump approx 1.5 ltrs
air cooled run very hot oil which degrades it quickly [around long term 50-70 hr service ]
air fuel ratio is between 10 - 12 to 1, constantly ,fine 4 mowers as they r under load 99% of time ,but less than ideal 4 the oil [higher rate of fuel contamination/ degradation ]

tomo:waving:

battags
03-04-2007, 05:06 PM
hello, air cooled kohlers 25 hp carby

run a very small sump approx 1.5 ltrs
air cooled run very hot oil which degrades it quickly [around long term 50-70 hr service ]
air fuel ratio is between 10 - 12 to 1, constantly ,fine 4 mowers as they r under load 99% of time ,but less than ideal 4 the oil [higher rate of fuel contamination/ degradation ]

tomo:waving:

Ok, I wore away a patch of my hair scratching my head, but I think I know what you were saying.....

johng
03-04-2007, 08:34 PM
its a 25hp kohler. runs fine, gas. i know oil turns dark doing its job of holding the dirt but this engines oil just gets black in like 4 hours of use. it runs fine and dont burn or leak oil. i just didnt know if there was a reason this one mower does this and my other 25hp kohlers dont. i run castrol oil. 10w30 im guessing it is just old slime build up n there.
well when i start cutting this season i am going to change the oil after every 5 hours like 10 times and see if that helps it.

Have you taken five minutes to check the compression? It's really one of the best tests to gauge the heath of your engine. Test it when hot and cold. I hate to argue with some guy who's dad ran a gas station and all but since it doesn't sound like this was an issue in the past you might be able to guess that something has changed. If you would rather change your oil every four hours instead without knowing what's causing the trouble have at it.
John...

johng
03-04-2007, 09:00 PM
In the event that you havn't done it before make sure that you do the compression tests at wide open throttle or they will likely read low. Leakdown tests are also very handy but require more equipment that a non mechanic might have. Compression gauges are inexpensive enough that no one who changes there own oil should be without one. You might also send your oil off to a testing lab. Likely it would be a less expensive option to four hour oil change intervals.
John...

tomo
03-05-2007, 03:05 PM
hello, which part of my response do u need assistance? Can not have u going bald ha ha !!

tomo:waving:

tomo
03-05-2007, 03:06 PM
hello, which part of my response do u need assistance with ? Can not have u going bald ha ha !!

tomo:waving: