diesel oil - is it always dark?

RussMan · Jul 16, 2009

I have a kubota I bought new in 06 and have about 160 hours on it - has been a wonderful machine. I changed the oil as recommended. But I notice when I check the oil level that it seems dark for being "new" oil - I fairly recently changed the oil.

My question: does oil in a diesel engine get dark quicker than in a gasoline engine? It looks like I should change the oil it is so dark but I know the tractor is not due for an oil change for a while. Since this is my only diesel I don't have the benefit of experience.

psj12 · Jul 16, 2009

Oil in a diesel will generally get dark quicker than in a gas engine. The color is not an indcation of the need to change oil. Time, miles or oil analysis should be used to determine change intervals.

RWEST · Jul 16, 2009

Like psj12 said, diesels tend to blacken-up pretty quickly. And, some diesel oils, Pennzoil "Long Life" 15-40 being one I noticed, come out of the jug very dark in color. Doesn't affect their ability to function properly tho..

In my experience, most mfr's recommended drain intervals are pretty conservative, so, either follow that, or get an analysis, and run it longer.

Key is to be sure you're running the proper grade/weight.

WH401 · Jul 16, 2009

When diesel fuel is burned in the cylinders, it creates soot, and eventually enough soot builds up in the oil to give it that black color. If you check the oil regularly on any diesel engine, you will notice that the oil progressively goes from its natural honey color to a black color. It's not a problem, it's just the nature of a diesel engine.

LBrown59 · Jul 16, 2009

RussMan said:
I have a kubota I bought new in 06 and have about 160 hours on it - has been a wonderful machine. I changed the oil as recommended. But I notice when I check the oil level that it seems dark for being "new" oil - I fairly recently changed the oil.

My question: does oil in a diesel engine get dark quicker than in a gasoline engine?
It looks like I should change the oil it is so dark but I know the tractor is not due for an oil change for a while. Since this is my only diesel I don't have the benefit of experience.

Bingo

valley · Jul 16, 2009

Why not instal a Bypass Filter. A filter that cleans a small amount of oil at a time, the bulk of the oil continuing through the system. A filter not inline with the OEM fliter. An oil cleaner.
On truck threads I have seen that they are intaled on large Deisel Engines some say the oil stays clear or nearly clear.
Some do it not to extend change time but to always run clean oil.
The only question is what filter to instal. Richard

WH401 · Jul 16, 2009

The problem you run into with a bypass filter on a tractor is space. Where do you mount it? The hood basically covers the entire engine compartment like a glove, and there's no way you want to mount it below the frame. Plus I don't know as that I would want to put a bypass on a tractor since a tractor's oil see's different mediums than a truck engine. Space is still the biggest issue though.

DieselPower · Jul 16, 2009

WH401 said:
The problem you run into with a bypass filter on a tractor is space. Where do you mount it? The hood basically covers the entire engine compartment like a glove, and there's no way you want to mount it below the frame. Plus I don't know as that I would want to put a bypass on a tractor since a tractor's oil see's different mediums than a truck engine. Space is still the biggest issue though.

Not sure what you mean by that? A bypass filter does not know the difference, solid particulate contamination is solid particulate contamination no matter what engine it is in. Be it a lawn mower, car, tractor trailer, ag tractor or industrial turbine engine the bypass filtration system serves the same purpose, remove as much debris from the oil as possible, some filters also remove water.

WH401 · Jul 16, 2009

DieselPower said:
Not sure what you mean by that? A bypass filter does not know the difference, solid particulate contamination is solid particulate contamination no matter what engine it is in. Be it a lawn mower, car, tractor trailer, ag tractor or industrial turbine engine the bypass filtration system serves the same purpose, remove as much debris from the oil as possible, some filters also remove water.

I guess mediums wasn't the correct word, perhaps situations would work better, such as excessive idling and oil not getting up to temp to burn off the condensation, and such. But yes, a filter is going to filter no matter what, I'm just talking about the situations that can affect the oil that a filter can't help with. But either way, unless he has a huge M series Kubota, maybe even an L series perhaps, I doubt if he'll be able to find a suitable area for such a bypass without it being in harms way.

DieselPower · Jul 16, 2009

You can get bypass filters that are fairly small. No need to install a huge one on a small engine. As far as mounting goes, it's only limited by how much oil line/hose you get with it and your imagination. It could be mounted behind a seat, on a fender and there's usually room under the hood if you use a properly sized one.

valley · Jul 17, 2009

I have a bypass filter, the size of a spin-on, a little longer counting the mount. I haven't mounted it yet.

curlysir · Jul 17, 2009

RussMan said:
I have a kubota I bought new in 06 and have about 160 hours on it - has been a wonderful machine. I changed the oil as recommended. But I notice when I check the oil level that it seems dark for being "new" oil - I fairly recently changed the oil.

My question: does oil in a diesel engine get dark quicker than in a gasoline engine? It looks like I should change the oil it is so dark but I know the tractor is not due for an oil change for a while. Since this is my only diesel I don't have the benefit of experience.

Yes, I owned many diesel vehicles before I got my 1st tractor. And the oil getting dark quickly was one of the 1st things I noticed when I started on diesels. My tractor and RTV are the same. Just a few hours of operation or miles and the oil is dark. Just change it at the recommended intervals (hours) and you will be ok.

RalphVa · Jul 18, 2009

New oil put into my 26 year old Benz diesel ALWAYS turned black soon as I start it.

The oil in my 2004 JD with nearly 400 hours on it doesn't get quite as black right away, but it does get a black tinge right away on startup.

It doesn't take much oil left in crevices to blacken the new oil.

Ralph

neucam · Jul 18, 2009

Good information, I too wondered on my Kubota that it did not take long for it to turn dark. I was worried I was getting other contamination in it. Now I won't worry too much about it.

eastexan · Jul 19, 2009

This brings up something that I've been wondering about.

Where I used to work, I went trough 2 Ford F-Super Duties that were meticulously serviced regularly at the Ford dealership. I was required to inspect the truck and check fluid levels every morning before work.
From the time they were new, the oil got black almost immediately after an oil change.
I bought an old Ford 3000 tractor 2 years ago, and was surprised that the oil looked clean. I figured it had just been changed before I looked at it. But it never did turn black, and I kept putting off changing the oil way past the point I should have. The oil just slowly turned dark, the way gasoline engines do over time.

I know there's differences between the old Ford tractor diesels, and the newer more efficient and cleaner diesels today. But do you think that the oil wasn't doing its job of cleaning the engine? That maybe the guy had a non-detergent oil in it. Or is that normal with the old Ford tractor diesels? I've thought too, that maybe the compression is a lot higher on newer diesels, causing the oil to get dark quicker.
I don't mean to sound dumb here, but I've only owned gas tractors before this one.

GreenLawnFarm · Jul 19, 2009

same here. b7800 oil changes black and keeps getting darker. haven't found it to be a problem. if kabota thought it was an issue they would have put more filters in the system. as i see it adding another filter is another hose able to come loose or get punctured. plus the added cost of another filter.

RWEST · Jul 20, 2009

But it never did turn black, and I kept putting off changing the oil way past the point I should have. The oil just slowly turned dark, the way gasoline engines do over time.

I know there's differences between the old Ford tractor diesels, and the newer more efficient and cleaner diesels today. But do you think that the oil wasn't doing its job of cleaning the engine? That maybe the guy had a non-detergent oil in it.

Hard to say what was in it before - some of the old-timers just grabbed whatever was lying around and dumped it in there..

You did put something diesel rated in, right?

eastexan · Jul 20, 2009

RWEST said:
Hard to say what was in it before - some of the old-timers just grabbed whatever was lying around and dumped it in there.. You did put something diesel rated in, right?

Actually, I haven't changed it yet.

I started to a while back, but started reading about all this ULSD/CJ-4 controversy. Now I'm wondering what oil to use in these older tractor diesels to get the best protection, since oil now (CJ-4) has lower levels of protective zinc.

I may post on the bobistheoilguy.com website and ask the pro's what they think.

WH401 · Jul 20, 2009

eastexan said:
Actually, I haven't changed it yet.
I started to a while back, but started reading about all this ULSD/CJ-4 controversy. Now I'm wondering what oil to use in these older tractor diesels to get the best protection, since oil now (CJ-4) has lower levels of protective zinc.

I may post on the bobistheoilguy.com website and ask the pro's what they think.

The ULSD/CJ-4+ oil controversy is a valid concern and I would refrain from using it in anything that is of the "pre-emissions" variant. John Deere's "50" brand oil is a 15w-40 that is still rated at CI-4+. If your tractor has less than 100 hrs than I would use that, mainly because of break-in. If the tractor has over 100 hrs than I would look into Amsoil 15w-40 Heavy Duty Diesel and Marine Oil. It's a fully synthetic oil and it's still rated at CI-4+. I changed the oil at 50 hrs on my 3320 and replaced it with some left over Shell Rotella-T 15w-40 rated at CI-4+, mainly just to help the rings seat fully from a regular dino oil. At 100 hrs I'll change it to the Amsoil. I have already had great success with the Amsoil in a few personal vehicles.

BrentD · Jul 20, 2009

I wondered about the oil darkening situation right after we purchased our little dozer. The guy at the dealership said he had just changed the oil and it was already black as pitch.

Reading this thread I got to thinking about the soot issue and wondering if it might actually contribute some lubricating properties to the oil... After all, we put powdered graphite into locks to keep them operating smoothly. Seems to do a really good job. And all the diesel soot I've ever encountered had an almost soapy feel to it.

Is there any hard data out there that would maybe prove or disprove this theory?