Dirty Oil After Oil Change?

This is an odd question but here goes. Last winter I had the oil changed in my Cummins 5.9TA's but was not present when this was done. When I got back to the boat 2 months later I checked the oil and the oil in the port engine looked clean while the oil in the starboard engine was dark. I mentioned this to the mechanic and he said it was due to the old oil still being in the oil tube and this was what was showing on the dipstick. We have only ran the boat a few times since for only a couple hours of run time but when checking the oil a couple of weeks ago the oil in the port engine still looks relatively clean and the oil in the SB engine still looks dark. I have the oil change system but not sure if this has anything to do with it. Did the mechanic only do one engine? He did get side tracked in the middle of winterizing it and maybe forgot what he was doing. Has anyone encountered the dark oil in one engine after an oil change? Thanks!!

It would be interesting to get an oil analysis and compare the two.

Sounds fishy to me. Unless the filters were not changed at the same time as the oil.

As CB says, fishy, very fishy.
Now, my oil when changed looks new until the engine runs a few hours and then looks dark, very dark.
But if the engine was not run, ...

Lesson learned, save the money and change the oil yourself.

Also, once you don't trust someone, don't go back again, if you do, it's on you, not them.

Sammy

Is this a new to you boat and the first oil change? How many gallons of new oil did you get charged for? Was a new filter installed? It is not easy to extract the last gallon on some engines, how was old oil removed? Is this a mechanic to be trusted?

On my engines there is always some residual oil left after pumping it out. I add a half gallon of new to dilute remaining old oil and pump it out again. Maybe the residual on one engine was more than the other.

I have found its very common and mostly a difference in on engine filter stules.

My 8V71 and series 50 will show black after an oil & filter change and a 5 min run to look for leaks.

The older 6-71 has a bypass filter , in WWII books its called a "colour filter" and after change the oil doesn't even get as tan as car oil for 50 hours.

For 25bucks you can sample the oil.

For 60bucks you can change it again.

We have two 6bta5.9 and I changed the oil and filters on both recently. The oil colour was nice and clean on both when first changed and is starting to go dark with use at about the same rate. As for the old oil still being in the dip stick tube this is rubbish. My guess is he only change the oil in one.

FF said:

I have found its very common and mostly a difference in on engine filter stules.

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You've found it common that when the oil is changed in a pair of engines in the same boat one will show clean light colored oil on the dip stick after the change and the other engine will show dirty or dark oil on the stick?

FF said:

I have found its very common and mostly a difference in on engine filter stules.

Click to expand...

You've found it common that when the oil is changed in a pair of engines in the same boat one will show clean light colored oil on the dip stick after the change and the other engine will show dirty or dark oil on the stick?

Seen this before. Can be one engine held more old oil than the other.

Can be the "dirty" engine was running at a higher load, causing its oil to load up with soot. Then with change, the really dirty remaining oil turned the new oil dark.

I'd just change it again.

I have always changed my own oil and never had one engine show "dark." I smell a rat...

With Ski on this one...I have run a bunch of twin engine boats where the dipsticks, cooler setups, even the list of the boat may have contributed to more dirty oil in one than the other.

I have changed my own oil after switching positions of the remote filter and shortening the oil lines...now it stays cleaner longer. Before, it was black by the end of the first day.

I'll take you guys word for it.

While I've seen the fresh oil in an engine/s get "dirty" shortly after a change after a couple hours of running, I've never seen the oil in one engine of a pair not look dirty while the other did after the same run hours.

thank you all for the replies. I will change the oil in both engines and go from there.

I used to DIY the oil changes, sucking out the old stuff via the L120 dipstick hole. Last time I had the marina mechanic do it. He uses a vacuum pump, one of those tall tubular things, and he leaves it connected overnight. He got much more old oil out than I ever did judging from how clean the fresh oil was, and stayed, for quite some hours.

"He uses a vacuum pump, one of those tall tubular things, and he leaves it connected overnight. He got much more old oil out than I ever did"

Allowing the engine oil to drain overnight would not be mu choice.

On a normal oil change the passages and OIL PUMP are still full of (old dirty) oil.

With an overnight drain you are assured of a real dry start for the first few seconds of operation, the usual drain removal method gives no dry start , but does leave a cup or two of "old dirty" oil.

For me a cup of old oil in 7 gallons of fresh is no big deal.

I have had this happen. On my 692s it was every time looked like you had not changed the oil.

Pure pleasure said:

I have had this happen. On my 692s it was every time looked like you had not changed the oil.

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In both engines or one looked clean and one looked dirty after the change?

FF said:

...Allowing the engine oil to drain overnight would not be mu choice.
On a normal oil change the passages and OIL PUMP are still full of (old dirty) oil.
With an overnight drain you are assured of a real dry start for the first few seconds of operation, the usual drain removal method gives no dry start , but does leave a cup or two of "old dirty" oil.....

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That`s a good thought.

For those with the desire to keep the oil clean , catch the "fines" that simply flow thru a std filter , bypass filtration could vbe a solution.

The rolls if paper towels stuffed into a can do not impress me , but the use of centrifugal lube oil filters does.

Happily they are made for big trucks so can be had at not Yacht pricing.

Still will be about $700 per engine plus installation.

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if you are new to doing your own oil changes, remember that you must fill the new oil filter with fresh oil before you install it. Other wise the oiling system will run dry for a few seconds as the oil pump fills the new filter.

tadhanna,
I do it too but it's probably a bit of a fettish and likely is of no benefit.
I thought for most of my life that on engines w the spin on filter sideways kept the oil after shutdown and while not running. I have such a filter screwed onto the side of the engine. When I bought the engine (repower) I installed a remote filter w the threaded end up thinking the oil would drain into the bilge w the OEM filter on the side of the engine. Had oily bilges from leaks to the remote filter for years. Finally tore it out and started using the standard filter. The first oil change w the side ways filter I got out an extensive aramada of paper toweles and rags plus a little tray that I hoped would catch most of the oil. When all ready I unscrewed the filter on as quickly as I could. There was no oil to catch. I was immensely pleased that my oil change was now so simple but worried a bit about the dry starts my engine was now going to experience. Needlessly I'm sure.

But how many millions of engines are built this way? And then there's the guys that think that w the standard engine startup the engine experiences high degrees of wear before the high pressure oil reaches the bearings ... and OMG the last bearing on the oil gallery. Just nonsense. If it did any harm they just would'nt build engines that way ... IMO.

There are some things that clearly seem to be thus but are really so. However when I'm presented w an oil filter that is mounted w the open end up I definitely fill the filter w oil. I just like to get things as right as I can but in this case it probably does no good at all ... but I still fill the filter w oil. And I put 25% of the oil in a sideways mounted oil filter as little or none drains out as the filter is screwed on. Especially if I'm quick about it.

So tadhanna I do it too. Remotely mounted vertical filters are typically larger (mine was) and longer periods of time without oil pressure at the bearings during startup so filling the filter w oil may indeed be worthwhile.

Another thing I always do is to pour a tad bit of oil in the "O" ring groove and wet the top of the oil ring w fresh oil. Leaks in the boat are much worse than leaks in your car.

Does anybody know of a quick lube oil change shop or station that fills the filters w oil prior to installation? I can't say "I have no idea" because I'm quite sure they just slap the empty filter on. I almost never go to those places as guys working at such places are very sloppy and careless re what I've observed and heard. Over tightening drain plugs is extremely common. It really applies that if you want the job done right you need to do it yourself. But sometimes even half-assed "professionals" have knowledge we don't.

it seems nice to fill filter but some are hard to get to and screwing on a big full filter is an opportunity for several hours of clean up.


I disconnect the fuel solenoid and spin the engine on the starter until pressure is up. Let it sit to cool after 20mseconds of spinning. Soon enough the pressure will come up.
If you have run the engine to mix up the oil then the innards are recently lubed anyway.

There are two reasons i fill the oil filter in my engine. The service manual for the 5.9B series directs you to do it. Second, I ran boatyards with service techs trained on Cummins, John Deere, Yanmar, Mercruiser and several others. In service schools they teach the tech to do this. Yes there are many engines with a sideways oil filter. Yanmar has several models i know of and so does Onan. In those cases I just add a bit of oil and hope for the best. You have to work with what is given to you..

LOOK in a NAPA cross reference , some filters have built in check valves that make changes less messy.

A car drive thru oil change will not pre fill the filter,,, BUT the engine is at operating temps and there is an existing oil film on the engine internals.

The few seconds of no oil pressure, the engine parts slide , rather than work with a cushion of oil from the oil pump filling the bearing..

And the drier (not totally dry) engine starts after a 100 to 200 hour oil change have as much likelyhood in damaging your engine compared to so much else that is more likely to happen, that a meteor strike is more likely to do it in

Another possibility :

You indicated that you have an oil change system. While I have one, I only use it to remove oil and refill at the top of the engine. The pumps though are designed to pull oil out and push oil into the engine. The mechanic may have sucked the oil out of both engines and then stuck the discharge hose in a clean bucket of oil flushing the hose and pump back into one engine. By the time he switched to the second engine, the hose and pump were clean. My oil change pump and hoses might have a quart of residual if I don't make a major effort to drain it all out.

Ted

If engines were damaged by the few seconds after a start without oil pressure, I would be rebuilding engines left and right. And I am not. Most of the engine I rebuild are due to water being where it should not be, and 99% of the time the bearings are perfect. Often they go right back in.

Ted has a good point about using the oil change system for a fill. First engine filled gets the dirty oil in the hoses. Could be it.

I pump out the old and pour in the new.

Ski in NC said:

Ted has a good point about using the oil change system for a fill. First engine filled gets the dirty oil in the hoses. Could be it.

I pump out the old and pour in the new.

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Good point...the distance fro. Eng to pump is a factor if used to fill.
I agree w ski and add via fill vs pump...not a big chore