How quickly does your diesel lube oil go black?

Simi 60 said:

I am installing a remote oil filter to my Kubota based genset
This will allow not only easy change but fitment of much larger filters
Oil has always been instantly black after change so it'll be interesting to see what results I get with a bigger filter.

Click to expand...

Could instantly black mean you didn't get all the old oil out? Or very high hours? My genset takes about 50 hours to trend from clear to darker and black by 100 hours. This is with a one gallon oil capacity on a Westerbeke 12.5.

FF said:

The black is called soot , but weather it is harmless or functions as fine grinding compound is unknown.

Click to expand...

It is not an unknown to oil companies and engine builders. When I first got into the heavy equipment business in the 1960s oil analysis, soot particle size, dispersants, soot clumping etc were much in focus for DD and Cat. The oil companies were quite successful in joint collaboration with the engine builders to extend both rebuild dates and oil changeout intervals. Not only was soot a marker, but another dozen or so "items" as well.

Filtration improvements, engine design, better fuel, oil analysis programs and smart operators all played a role. Improvements continue. Sales, costs, warranties and equipment uptime are measurable and competition is fierce.

Advances in on equipment monitors, computer controls and maintenance detailing have today's industrial engines running longer, increased oil change intervals and generating more continuos HP per CC than just a few decades ago.

Doubtful any of this is relevant to our little low use recreational engines though. Change oil and filters regularly, sure use some bypass techniques but remember soot dispersant decreases as your oil ages. If you're lucky enough to have a commercial rated engine, treat it to fresh oil and it will last a very long time internally.

But then for that pesky sea water side -----

It takes over 100 hrs for the oil in my Lehmans to turn dark and even then not really black.

Ken

sunchaser said:

Could instantly black mean you didn't get all the old oil out? Or very high hours? My genset takes about 50 hours to trend from clear to darker and black by 100 hours. This is with a one gallon oil capacity on a Westerbeke 12.5.

Click to expand...

Sludge buildup I would suggest.

I dont know the genset history.
It has 565 hours on clock but was installed in a position which made access to filter and sump plug difficult, I am rectifying that problem with remote filter and tap on sump plug at next change, due now.

Genset did have an auto shutdown due to low pressure first time we used it for longer than 30 minutes so I wouldn't be surprised if it had never been changed until we got it as it was pretty thick.

Hasn't missed a beat since we changed oil and filter and sorted a few minor maintenance issues.
Probably should run an engine oil flush through it before dropping the next lot.