What’s The Best Way To Clean Dirty Engine Oil?

I never change my oil based on mileage or hours but by smell and colour. I usually change the oil enough times to get to "know" the engine on any vehicle I buy. My 1986 350's with about 1400 hrs stay clean (yellow stain on oil check rag) for about 50 hrs before blow-by starts to discolour the oil so I seldom run them over 50 hrs between oil changes. Anal and persistent changes up front should clean the carbon deposits to where you can judge oil change need by checking your dip stick. This would be a rather expensive method for diesel owners though
 
I have always found at 25 hours the oil starts to discolor but by 50 or so hours it usually is pretty dark.
 
Top*prop,

Tell them they need to change their own oil if they think they can do a better job! :)

Don't you just appreciate folks that can tell you how to do your job better than you, and they've never gooten their hands dirty?
 
I agree with your comments, but from a customer's point of view, with everyone trying to screw everyone else out of a buck these days, you have to look out for #1 or you'll end up stepping in #2. Bottom line - Try to be understanding, explain to them the possible causes and re-assure them that you perform the services requested and paid for. It's tough being a consumer out there right now - especially in the boating world.
 
Last edited:
When I winterized my engines a week or so ago I changed the oil and before running them the oil was close to black. I got around 4 quarts out of each as well.
I ran one engine to warm it back up, changed the oil again and it was still close to black, no real change.
I know I have new oil in them now but it is a bit disconcerting.
 
Coram Deo said:
When I winterized my engines a week or so ago I changed the oil and before running them the oil was close to black. I got around 4 quarts out of each as well.
I ran one engine to warm it back up, changed the oil again and it was still close to black, no real change.
I know I have new oil in them now but it is a bit disconcerting.
Click to expand...

Now you know how I feel. The only difference is that you know when you changed the oil last time. In my case I just purchased the boat and can only go by what I was told, which doesn't mean the info is 100% accurate :huh:.
I didn't run the engines to warmup the oil and I was able to get about 5 qrts out. I also know that I have nice and new oil with performance filters. Just to sleep better, I'll do another oil change after few hours.
 
I changed my oil this past weekend, then ran 125 miles. It's still amber. I ran the port engine for about 15 minutes at the dock while I prepared all of my tools. Immediately upon shut down, I began pumping the oil out while loosening the cap and punching a hole in the filter. After it was all out, I let is sit for about 5 minutes, then pumped out more.

After that, I put an old towel down in the bilge, and got one of my wife's good tupperware containers (1 qt, round), and placed it below the engine. I removed the drain plug and removed about another 8 oz. In the bowl, the oil looked dark brown. When smeared on a paper towel, it looked dirty-amber. After running for about 6 hours, the new oil looks fairly new on both engines.

I also soaked up all of the old oil in the filter-mount with paper towels.

The drain plug on the 8.1 Horizon S is on the boat's stbd side (engines mounted backwards with V-Drive). The port plug is right there near the center of the bilge where the stringer dips down in front of the engine mounts. The stbd one is harder to get to as it's outboard of the engine and it's in an area where the floor slopes up toward the side of the motor (V-bottom slope).

I will definately follow these steps on all subsequent oil changes. If practical, I recommend everyone try to get out as much of the old as possible.
 
Alex a good check (which may help you sleep better) is to have oil analysis performed on the oil. Oil analysis is kind of like the doctor taking blood from your arm to run tests.... and ensure all is well. They test the oil for various things... which can indicate what, if anything, is amiss with the motor(s). You would want to collect the oil sample at oil change time after you put the "normal" amount of hours on the oil.

I personally use Blackstone Labs but there are many good labs out there that perform this service. http://www.blackstone-labs.com/

As for getting the oil clean.... if you are on land I have had good experience with using the remote drain hoses that are usually tied to the bilge plug (and the bottom of the pan on the other end). I warm the engines.... then let it drain for about 2 hours pouring in a quart of clean oil to flush out the bottom of the pan at about 1 hour. I take care of other maint items while waiting for the oil to finish draining.
 
Jeremy,
Thanks for good suggestion. In the spring I'll try the simple method first (run it with new oil and change it after few hours of use). I may do another mid season oil change and keep an eye on how it is. If the oil would get dirty right away it'll be the time to contact the lab (hope I wont needed).

Thx,
Alex.
 
Alex F said:
During the first introduction to our 320DA I’ve checked the engines oil and noticed that it’s was dirty (black), but the it didn’t feel like it lost it’s quality, just the color. I’ve seeing oil in this condition few times in cars and simply changing the oil with filter fixes most of the discoloration. So, when we purchased the boat I’ve changed the oil and installed performance (larger) filters. After that I ran the engines for about 10 minutes and when I checked the oil I was very surprised to see that the color didn’t become any lighter. So, I got few question:

  • What would make the oil get so dark other than not changing it on time?
  • What would be the best way to restore the clean color? I’m thinking that it would take about 3 (2 to flush and 1 final) additional oil changes, which is about 11 4gal. bottles to do both engines. Would anyone any other than Quicksilver SAE 25W-40 (based on the manual this is recommended oil) just for flushing it or should I just eat the cost of over $200?
  • Would I have to change the filter again, or by flushing it with new oil will keep the filter clean?
So far, my plan is to drain current oil (leaving new performance filter unchanged with the assumption that it’ll get cleaned with every fresh oil I put in), refill and run the engines for 5-10 min. Then repeat the same steps until the oil is clean (hopefully, no more than 3 times). Does it sound like proper way of handling this?

P.S.
When I checked generator the oil was a little dirty as well, but as soon as I changed the oil with filter and ran the genny for 10 min. the color of the new oil remained crystal clear.

Thanks,
Alex.
Click to expand...

Alex I have the same issue with our twin 8.1S engines. I have been changing the oil every 20 or so hours in the past two seasons and it is right away black again. The engine is clean inside though. I figure they just run dirty. My 5.0 MPI did not do this and the oil stayed clean for about 10 hours, then began to get black too.
 
Alex D,
Thanks for heads up. Sounds like I could be waisting time with the oil changes. Every 20 hours it does sound too often to me. I was advised to use special cleaner, which can be purchased in most auto parts stores. Did you try any of the cleaners? I think I'll contact mercury, I'd like to hear what they suggest.

Thanks,
Alex.
 
There is a product that can be purchased only on the web. It is called AutoRX and is added to the oil. www.auto-rx.com This is a gentle ester cleaner that can be in the oil permanently. A stronger cleaner I have also used for the last five hours before an oil change is LubeControl www.lubecontrol.com I have used both of these and they are highly recommended by auto enthusiasts and on the www.bobistheoilguy.com oil forum, which is a great resource for all lubrication questions..
These will dissolve slight dirt in the engine very gently and without risk of clogging the oil passsages or else. If your engine however just runs dirty, they won't make a difference except keep the deposits from accumulating.
 
You must log in or register to reply here.

Forum statistics

Threads
113,120
Messages
1,426,612
Members
61,037
Latest member
wojozobl
Back
Top