Oil Color

[Gomez]

I just changed the oil and filter in my B2400 over the weekend. The oil seems to get black very fast. I put about an hour on the unit since I changed the oil, and now the oil is about as dark as the old oil was. Is this the way it is with diesels?

 

[Bird]

Gomez, unlike gasoline engines, I've never seen a diesel engine in which the oil didn't turn black awfully soon after a change. Sounds normal to me.

Bird

 

[W5FL]

The oil in my new Kubota was so clear it was nearly impossible to check on the dipstick. After 25 hours of operation it is possible to just see a little color in the oil. After how many hours does the very dark color start and where does it come from?

 

[PaulB]

Couldn't agree with you more. I found the same thing with my 1700, and I GUESS the oil works just fine even when it looks dirty, but now that i went synthetic I don't have to think about it anymore - mine looks like it came out of the bottle after 15 hours so far.

 

[Bird]

On a brand spanking new engine, it does take awhile before the oil turns dark, but on all the changes thereafter, it'll turn dark very quickly. Or at least that's been my experience with diesels, and that of other people I've talked to. Now, PaulB says that synthetic oil stays looking cleaner longer. Can someone give me a scientific reason for that? Or even a wild guess?

Bird

 

[PaulB]

Nope. But I swear on a stack of bibles it is true, based on my observations at 15 hours of use so far. If it changes as the hours add up, I will post on it.

 

[MChalkley]

PaulB, I predict it will change to get about as dark as the petroleum did. In most, but not all, engines, synthetic doesn't seem to get dark as quickly as petroleum does, but I don't know why this is, or even if it's a confirmed fact.

I do know that the black stuff doesn't hurt, and there are many who say it has a 'plating' effect that prolongs the life of the engine. I also know that a .5 micron filter will not take it back out, and a centrifuge-type filter won't remove enough of it to change the color of the oil, so the stuff is very small and light.

 

[Anonymous Poster]

An important function of engine oil is to keep the particles that are too small for the filter to remove in suspension in the oil. This stuff will then be removed at the next oil change.
If synthetic oil does not get as dark as regular oil under the same conditions, then it must not be doing it's job holding these particles. This would allow the crud to build up in the crankcase where, in the future, a large amount of it could be released all at once causing a problem.
All modern oils that I know of are very good at holding particles in suspension. The clean oil in the post above, is most likely due to how new the tractor is.
This just goes to show how testimonials about how good or bad a product is can easily be influenced by unrelated factors. Most if not all the things said here about synthetic oil, with the exception of it's cost, fall into this catagory. Claims about a product are only meaningfull if there is a large enough sample tested under controled conditions.
My personal favorite (sorry Mark) is the claim that synthetic oil significantly increases the life of head gaskets in Volkswagon Rabbits. This was "proven" by comparing several synthetic lubricated Rabbits to several Rabbits using conventional oil. If I remember correctly the synthetic Rabbits head gaskets significantly outlasted the others... conclusion it must be the synthetic oil. Much more likely is that the owners of the Rabbits willing to pay the extra cost of synthetic oil took better care of their cars and torqued the head bolts or performed other maintainence more often, resulting in increased life. Without a controlled test we will never know the real reason.

Andy

 

[MChalkley]

It's impossible, as you say, to prove or disprove such claims, but, unfortunately, your claim falls into the same category. I can tell you of my experience. In all the VW diesels my father and I have owned (except my current '96), none of them have less than 250k miles and several more than 300k, one over 400k, none of them ever retired due to engine failure, none of them ever even had any engine maintenance other than routine timing belt replacement, none of them have ever had the heads retorqued, not even once, none of them ever had the valves adjusted (though the early models 'required' it as routine maintenance), none of them even had the oil changed more often than once a year. I don't think this would qualify as 'better care' or more frequent maintenance in anyone's book.

I don't think the synthetic has anything to do with the head gasket directly, personally. It's the increased heat handling capability that does it, I think. At any rate, it clearly is the oil and not the maintenance.

The fact of the matter is, in my opinion, that most people who refuse to look at the fairly obvious evidence of synthetic's superiority in the form of their specs, will also dismiss the controlled tests you speak of, as well. I don't know why, it's just the way it is. I hope never to be so closed-minded myself. (My prejudice against GM products excluded, of course.)

 

[gordon]

Black oil is the nature of the beast in a diesel nothing to be alarmed about. I have always used regular oil in my diesels changed at normal intervals and have logged many hours without an oil related problem---One of my current kubotas has over 7000 hours on the engine with a very small amount of blow by but runs like a champ.