Is diesel oil always black instantly?

[iancoombe]

A friend put diesel/gas conversion on his hz 75 landcruiser his oil stays clean and has extra power on demand. So the black is probably related to power demand and with the gas injection you probably get a clean burn at high demand, but it would mean another fuel to source.

[Rorzech]

My buddy had a towing business. All his trucks were diesel. He lost quite a few engines using ordinary oil. Then he switched to full synthetic.Three years later out of habit and number of miles ,he pulled one of his diesels in to rebuild the engine.To his surprise he could still see the cross hatching on the cylinder walls and when he measured the bearings ,they had only 0.0001 of wear on them. That's a tenth of a thousand's of an inch. Since it was apart he changed everything anyways. I saw that with my own eyes and it was enough to make me switch to full synthetic oil. As much as I abuse my diesels they've never let me down due to oil issue related problems. I've never had any with gas or diesel engines. A few extra bucks for synthetic is worth big bucks down the road. I didn't need to buy into synthetic oil , the proof was staring me in the face.

[a64pilot]

Likely his Diesel was a turbo and saw a hard life with high oil temps towing etc.
Most of our little Diesels are NA and don't work hard at all. The HP per cu in will tell the tale. If it's well less than 1/2 a HP per cu in, then it's not being pushed real hard.

On edit, I am a card carrying syn oil man myself, everything I have owned for the last 40 yrs has run syn oil except my airplanes and now my boat. No syn oil for aircraft, and the boat I don't think it's an asset, but that is just my opinion.

[model 10]

Originally Posted by a64pilot

No syn oil for aircraft,

Come on, what kind of aircraft are you talking about? An airliner would not get off the ground with mineral oil.

[a64pilot]

There is no synthetic aircraft piston engine oil, there are blends but no syn.
Yes, I assume 23699 is synthetic, however I have never owned a turbine, have thousands of hours in them, just never had the bucks to own one.

https://generalaviationnews.com/2005...craft-engines/

[Lepke]

The grade of diesel, quality of oil filtering system and engine design have the most effect on oil transparency. Older engines with bypass filters actually cleaned the oil better. The slower the oil goes thru the filter, more smaller particles are caught. Most spin on filters are made in 3 lengths. Use the longer one for cleaner oil. Also past diesel formulations burned better. Low sulfer diesel doesn't burn as hot or completely as the previous fuel. Not burning as well or hotly means you burn more fuel for a given rpm. That creates more soot in the oil.
The fuel additive I use is a biocide and also enhances burn. I get about a 10% fuel savings and my oil stays cleaner. My old Detroits use a bypass type filter.
I centrifuge my oil about every 100 hours. I can maintain transparency indefinitely.
When I change my Ford diesel truck oil at 5000 miles it still has some transparency. Thinking of adding it to the centrifuge cycle.

[model 10]

[QUOTE=a64pilot;2434131] just never had the bucks to own one.

That is not really true. You could buy a Fuga Jet or maybe a MIG, or some other eastern european jet for less money than your boat.

[transmitterdan]

Buy? Yes. Fly and maintain it? Probably not.

[poiu]

Originally Posted by a64pilot

There is no synthetic aircraft piston engine oil, there are blends but no syn.
Yes, I assume 23699 is synthetic, however I have never owned a turbine, have thousands of hours in them, just never had the bucks to own one.

https://generalaviationnews.com/2005...craft-engines/

The Rotax aero engines allow certain synthetic car oils only when used with unleaded fuel and if temperatures are higher than 120C. i.e. In practical terms close to never. They do recommend certain semi synthetics though as a preferred choice.

For most of our old boat engines, which run cool, mineral oils give better lubrication in the form of higher film strength and give better engine cleaning than synthetics. They also give a much higher film thickness on start up. I won't use a synthetic in my Perkins.

It gets black quickly too, a bit straight away, then totally black in 20 hrs.

[a64pilot]

I have a friend with an L-39, he often goes to air shows with it, cause for showing up, they fill his tanks.
Many of those aircraft the TBO is incredibly short, and the Communist way of thinking when they were designed was frequent engine replacements and the engine go back for remanufacturing, not much on wing maintenance was done.
Reason they are so cheap is you can't afford to own one, the proverbial White Elephant.

Small twins are to some extent in the same league, burn twice as much fuel, cost twice as much to operate, but don't carry much more or go much faster, and the perceived safety of the extra engine is not borne out statistically. So you can usually buy a twin for less than a big single.

[ValiantV]

Originally Posted by 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.

Oh, not the color of the oil matters to me, just more concerned that black oil is the sign of a dirty engine - one that's been neglected or might indicate problems on the horizon.

As for oil color, sone years ago there was an auto oil that contained graphite. It was black when it was new. Funky.

V

[a64pilot]

Actually black oil to some extent signifies a good high quality oil.
Good oil will hold the soot in suspension so that on oil change the soot goes with the oil, cheap oil will stay clear somewhat as the soot settles out in the pan. One of the most valuable qualities of a Diesel oil is its detergent package and its ability to hold soot in suspension.

[beirutsailor]

The Yanmar manuals say that you should run your engine at top revs every three hours for two minutes. If you do, you will see your hull take a nice black area around the exhaust. That means you cleaned the engine. Too many yachts show pristine exhausts, running too slow to get the gunk out. If you do this revving before the oil change, the oil will stay clearer longer.

[lordgeoff]

Originally Posted by lazydove

I bought a brand-new Volkswagen Tiguan (one of the cheaters). The oil was pitch black after about 20 hours of use and turns black a few hours after an oil-change. Volkswagen claims that this is normal.....but can we still believe those guys?

I would trust VW way way way before EPA.
Nice to see that swamp getting drained....

[Cabo Jim]

I flush my Yanmar 4JH4 everytime I change the oil and filter. Oil is cheap! I pump out the old oil when the engine is hot, and drain the oil filter and put it back on. Fill with 4 litres of new flush oil and run the engine, check the oil pressure and run for five minutes. Pump out the flush oil (just as dirty as the old oil), install the new filter and oil. Your engine will last for many, many more hours.