Is diesel oil always black instantly?

[JimsCAL]

I agree with comments about the difficulty with getting all the old oil out when doing a change. I use one of those hand pumped units that create a vacuum suck the out the dipstick tube. On the Universal on the previous boat, I always had a little old oil left the the oil was black after the first run. On my current boat, the Yanmar sump seems to be such that I can get almost all the old out and the oil very slowly gets black over the course of the season.

[Stu Jackson]

Add that diesel engines in boats are not like cars that can be put up on a lift to drain the oil. Engines are at an angle, and not all the old oil can be removed. Black: Universal M25, 3,200 engine hours, owned 19 years since 888 engine hours, always been that way.

[Stu Jackson]

Originally Posted by sailah

But the problem is now storing it. In a plastic bag it leaks the residual oil and now the pump is coated.

Easy: put it in TWO (or more) bags.

[Diesel Bill]

I would be more worried if the oil didn't get dark after 25 or so hours. The oil in my 5.9 Cummins looks clear on the dip stick but when I drain it into a plastic bucket I can see how really black it is. Stains my hand and rag.

[model 10]

Originally Posted by Diesel Bill

Stains my hand and rag.

What about your shirt and maybe your pants too. It does not come out either.

[Wotname]

Originally Posted by Stu Jackson

Easy: put it in TWO (or more) bags.

Yeah but....

That doesn't stop the exterior of the pump getting coated which is the concern sailah has (AFAICT).

[Wotname]

Originally Posted by Guy

What about your shirt and maybe your pants too. It does not come out either.

You need shirt and pants gloves...

[sandy stone]

I always expected my engine oil to turn black right away, as you say. But on my current boat, with a 1986 Volvo 2003 engine, the oil stays amber for months. I'm as surprised as anyone. I change the oil every year, whether it needs it or not, and I put a half quart or so of new oil into the crankcase while I'm sucking out the old oil. Maybe it helps, I don't know, at least I feel good about it. The engine internals that I can see through the oil filler port look absolutely spotless. I do use Rotella, and try to stay with Wix filters.

[Rapanui]

2 off Yanmar 3YM30, oil changed on laying up last autumn, 8 weeks use to date and still almost clear, a very light straw. Fairly confident that it will be the same on laying up this year as last.

[Sandero]

On my 32 yr old Volvo MD 17D it goes black pretty quickly but not immediately after running. When I check the oil level after a change and a short time it is pretty light colored.

As long as it does the job... who cares the color? I've been doing regular and somewhat frequent oil changes for 32 yrs and the engine works fine. It's been aging well... wish I could say the same about the skipper.

[transmitterdan]

Originally Posted by Stu Jackson

Easy: put it in TWO (or more) bags.

He means the pump gets oily and slippery inside the bag.

I keep some cheap Harbor Freight oil absorbent cloths handy and ty-wrap one around the end of the hoses of the hand pump. Some oil drips out but the cloth absorbs it and when it gets saturated I replace it.

[sailnow2011]

Originally Posted by ValiantV

Hi cruisers,

Been working on gas engines for years, but new to diesels. I've always heard that crankcase oil in diesels is pretty much black right away because diesels create more unburned carbon than gas engines. I have no idea if that is truth or urban legend.

Having bought an older boat, and this, no real idea how often the POs changed oil, mine is black now.

With a "dirty" gas engine, performing a couple of short-interval oil & filter changes can often clean out the gunk and leave you with oil you can see through for several thousand miles. Is this possible it even normal for a diesel?

I figure I'll do a couple of closely-spaced oil/filter changes anyway, but wondering what to expect. Any insights would be welcome!

There are 3 main engines in use today.
Butane (propane) the oil in these engines looks brand new even after 100's of hours. The butane produces very little soot. Its a light fuel.
Gasoline (petrol) Make the oil darker within a few dozen hours.
Diesel makes the oil go black in a few hours. The soot on the cylinder liners goes into the oil right away. You could add bypass filtration, Some do, but its a waste. The blackness of the oil doesnt hurt the engine. With a full synthetic you could go a thousand hours between changes.

[Gone2long]

Originally Posted by ValiantV

True, not being able to drain (as) completely as in a car means you start out with "mostly" new/clean oil. Still trying to find the best way to drain oil without making a mess.

Yeah, me too : ) Older 3GM30 Yanmar. Black oil, even right after a change. I blame the residual oil mostly. Seems a way of life : )

G2L

[Gone2long]

Originally Posted by sailorboy1

So people are looking at it wrong. The oil is black so can see the level on the dipstick

Do not fear. There is sympathy for your logic, plus housing and work for folks like you in the Philippines : )

[a64pilot]

Originally Posted by sailnow2011

With a full synthetic you could go a thousand hours between changes.

Assuming you had extremely efficient bypass filtration, and you kept doing analysis to keep an eye on the oils TBN, maybe.
Now if it took more than a year to put a thousand hours on it, unlikely the oil would have enough TBN to get it through more than a year.

In truth it's not at all unlikely that you could do that with a good non synthetic oil, most of our little motors run the way most of us run them are not hard on oil, it's the soot and acid from water and combustion by products that trip an oil change. Seeing as how there is so much moisture in a marine environment, I'm betting the oil would become acidic before a thousand hours and need changing.