My Engine Oil is Staying Suspiciously Too Clean

[rardiH36]

I'm pretty sure that after previous oil changes for my Yanmar 2QM20H engine, the oil took on the typical gray/black appearance for diesel engines.

This time, even after about 40 or so hours, the oil is staying gold color, almost as new. Its probably nothing, but I'm suspicious and thought to get feedback from the forum.

The engine is running great.

The attached photo is of a paper towel I used to wipe the dipstick few times. To the right of the red outline is clean white paper. Inside the outline is the oil smear. (And also to the left of the outline since I didn't draw too well on that side.)

Other background that might be useful for the analysis:

- The oil filter is direct from the Yanmar dealer. This last time, they gave me one that physically is much smaller than the type that preceded it. However, supposedly this one has equal or better performance than the old type. Also on the filter topic, the Yanmar service manual allows that an oil filter can go 2/3 oil changes. I don't go try to go for all three allowed uses; but this is the second go-around for my current filter.
- I did have thoughts that maybe the oil pump wasn't doing its job. To check, I revved up the engine and while running, the oil level in the pan fell to the very bottom of the dipstick. I believe this indicates that oil is being sucked up and distributed around the engine normally.
- This Yanmar originally a seawater cooling design. But it was converted to anti-freeze self contained cooling with the addition of an external heat exchanger. However, because the 140-150F thermostat fitting on the exhaust manifold assembly remains, this engine runs much cooler than most.
- Since buying the boat about 4 years ago, I've changed the oil 6-8 times. I suppose its possible that if the previous owners had let the oil get very dirty, its taken this much time to finally cleanse out all the old gunk?

So, should I be concerned?

 

[Ted]

Wow, that is really clean oil. I change my oil and filter at the end of every season. I never use it for more than 40 hours per season but the oil is definitely darker than yours. If my oil looked that way after 40 hours of use, I would begin to wonder if it was actually circulating. I also use the Yanmar filters and the first time I saw the new smaller style I thought it was a mistake. Triple checked to make sure it wasn't. I never saw oil come out of my engine that clean, even after changing the oil and checking the dip stick after running the engine for only a few minutes. I would like to hear what others have to say but if it were my engine I'd be suspicious knowing what my oil usually looks like. Hope I'm wrong. I just can't imaging a diesel engine running without proper lubrication for 40 hours so this doesn't make sense to me.

 

[CalebD]

There are some filter experts here who can comment about the use of the new filter.
I'd comment that it is very proactive of you to even ponder this question and offer my own subjective remarks.
In my limited experience with a friends M-25 diesel I'd say that the oil in his engine gets pretty dark, pretty fast after an oil/filter change. That said I am certain my friend could stand to change his oil as often as you seem to - so kudos for that. I'd also guess that 6 - 8 diligent oil changes in 4 years may very well have helped to get out much of the residual black oil that often remains between oil changes. Perhaps you are also just more efficient with your methods of changing the oil then the PO. If the new, smaller oil filter is more efficient then both the frequent oil changes and the new filter are helping you keep your oil cleaner. You may be able to verify how efficient the new oil filter is once you remove and replace it on your next oil change.
I don't have a diesel in my boat (Atomic 4) but I too believe that older engines really like to have clean oil circulating in their lubricating passages.
BTW, if you think your engine is operating at too low a temperature you may likely be able to get a higher temp. rated thermostat for your 'fresh water cooled' engine. I think a 140 degree T-stat is designed for raw water cooled engines and there should be a 160 or 180 degree T-stat you could use instead.
Another factor can be how long you typically use your engine and if it is able to get up to its optimal running temp.
Good of you to be looking out.

 

[Rich Stidger]

Different engines but similar results....

FWIW, I have a Volvo MD22L, 50hp, 4 cyl in my h40.5 and the oil always seems to be very clean with a golden color. At an oil change at 125-150 hours, it is a bit dirty but not what I would call black.

In contrast I have a Westerbeke genset with a 3 cyl engine that runs at 1800 rpm and that oil becomes black after a couple minutes of running after an oil change.

I never could understand why these had such differing oil colors with exactly the same SAE 30 diesel oil.

 

[monkeybars]

as a cummins mech i can tell you the filter has nothing to do with it.carbon or soot is smaller than a half micron in diameter.even the best of oil filters only filter down to the 15-20 micron level.it mostly has to do with injection timing.the new cummins engines have injectors that inject three seperate times in one compression stroke.the last one being very late which is to aid in lowering NOX emmisions for EPA requirements.these engine will have totally coal black oil in less than two hours use versus the pre 2003 enginies which could keep the oil honey colored for 50 hours.

 

[rardiH36]

Thanks the responses. Somewhat relieved to hear that oil color doesn't necessarily have to go blackish.

For Ray: Given that oil color is affected by injection timing, and that I have observed a change, do you think that I should check/adjust the timing? My mid/late 70's designed Yanmar certainly will be very low tech compared the Cummings engines you refer to. I had been thinking about checking the injection timing at some point since I have read that out of spec injection timing can also cause an engine to shake more than normal on its engine mounts. The 2QM20 supposedly is prone to vibration, which certainly mine does. But at select rpm ranges, the engine movement does settle down. So there hasn't been a pressing need to check the timing.

For CalebD: Re increasing the operating temp. A couple of years ago I did ask a Yanmar repair shop about using a higher temp T-stat. So we do think along the same lines. It seems however that the thermostat housing on my engine will only match the size and profile of a 140-150F T-stat. Makes sense I guess. For a saltwater direct cooled engine, things wouldn't go to well inside it if an owner inadvertently or purposely installed a 170-190F thermostat. I've read that minerals and salt will precipitate out and adhere to and block the water channels inside an engine block operated at higher temps. So Yanmar made sure the wrong T-stat couldn't happen. Since my engine has performed well at the lower temp spec for 30 years, with this information, I lost interest for a higher temp work-around.

 

[okawbow]

This is very timely for me. I recently rebuilt my 44 year old Albin diesel. I've ran it under load for 10 hours now to seat the rings. The oil is so clean, it is difficult to see on the dip stick. Before the overhaul; the oil would be black after a couple hours.

I'll check the injection timing next time I'm at the boat. The motor does have a little more diesel "knock" than before.

 

[CalebD]

rardiH36,

I'm no Yanny expert by any means but is it possible to change your thermostat housing so you could use a different T-stat? I know that an Atomic 4 is not a 2QM20 but I have seen some of the same external engine components used on diesels as my A4 uses. That said, Moyer Marine (which is A4 specific) sells T-stat housing replacements as well as a variety of T-stats. Check out the T-stat related parts they sell on this page:
http://www.moyermarine.com/cgi-bin/...all&template=Templates/B000_storebuilder.html
Someone with Yanny experience could tell you if this idea is even feasible.
This forum is great because of the breadth of knowledge of the members.
Ray's input was extremely helpful for example. I'm not sure why Benny deleted his post as he usually has something pithy to add.

 

[rardiH36]

Hi CalebD:

Thanks much for the link. At this moment however I'm getting ready to temporarily transit from my normal haunt to an alternative location. (During the winter months, I sometimes I drop out of the sailing mode to go skiing.) So I'm not able to study the link right now in much detail. I'll let you know ...

regards,
rardi

 

[RAD]

When I bought my boat the over all cleanliness of the engine inside and out compared to the rest of the boat was filthy and I started replacing the oil filter twice in a season to get the engine oil cleaner so after a few years it definitely made a difference...its not honey colored but a dark brown vs black after 50-60 hrs and if I do a long trip it does get darker.
I have a friend who has a MX25 universal that is 23 yrs old and he does the same routine and his oil looks as clean as the day he put it in

 

[jibes138]

It doesn't take much black to discolor the new oil. When changing oil you can only get so much of the old stuff out and the new oil mixes with a little of the old oil. If the old oil is very black the new oil will start its' life already a little discolored.

 

[RAD]

It doesn't take much black to discolor the new oil. When changing oil you can only get so much of the old stuff out and the new oil mixes with a little of the old oil. If the old oil is very black the new oil will start its' life already a little discolored.

Thats probably the answer.....I can only get the oil out via inserting a small hose inside the dipstick tube and I probably always leave about 1/2 quart in, I never tried putting a hose over the dip stick tube and drawing the oil up, maybe I'll get more out?

 

[Bill Roosa]

diti Jibes138
On some engines the dipstick allow you to position the suction tube so that almost all the old oil is removed (the 40.5 is a good example) on others not so much and some oil remains. So raidiH36 has the former (congrats).
you would also have to change the oil filter to get clean oil for more than a few moments.

 

[captron]

Oil weight??

Rich,
I have the same engine you have and I noticed that you use 30wt?? I was going to change my oil this past weekend and noticed that Marine Parts Express sent me the wrong filters, (have reordered) my question to you as I know you have had your boat for a while 1997, have you always used 30 wt?? which is what i used on my old boat a 1993 37.5 with a yanmar,(had for 16 yr's no engine problems) sold it and bought a 97 40.5,
but i think the engine manual ( if you want to call it that) specified 15/30 wt?? I think?? Any comments??

FWIW, I have a Volvo MD22L, 50hp, 4 cyl in my h40.5 and the oil always seems to be very clean with a golden color. At an oil change at 125-150 hours, it is a bit dirty but not what I would call black.

In contrast I have a Westerbeke genset with a 3 cyl engine that runs at 1800 rpm and that oil becomes black after a couple minutes of running after an oil change.

I never could understand why these had such differing oil colors with exactly the same SAE 30 diesel oil.

 

[Rich Stidger]

Rich,
I have the same engine you have and I noticed that you use 30wt?? I was going to change my oil this past weekend and noticed that Marine Parts Express sent me the wrong filters, (have reordered) my question to you as I know you have had your boat for a while 1997, have you always used 30 wt?? which is what i used on my old boat a 1993 37.5 with a yanmar,(had for 16 yr's no engine problems) sold it and bought a 97 40.5,
but i think the engine manual ( if you want to call it that) specified 15/30 wt?? I think?? Any comments??

I have always used straight 30W weight oil that is diesel rated. According to the Owners Manual for the MD22 and the Instruction Manual for the 22 Series, both have the attached oil weight chart. The 10W-30 and 30W are both good up to 104 degrees F, but the 10W-30 is good down to about 0 F while the 30W is recommended down to about 41 F. I stop boating long before it hits 41 F and I think that a straight 30W is a more stable oil than a 10W-30. The explanation that I have heard 30-40 years ago (maybe it doesn't still apply) is that a 10W-30 oil is really 10W oil with additives to keep it as thick as 30W when it is hot. They used to say if the additives broke down, all you had was straight 10W oil. That is why I use the straight 30W.

For my Westerbeke genset the recommendation is 30W, 10W-30, or 15W-40 above 68 F, and 10W-30 or 15W-40 between 41-68 F. I guess I should have been using 10W-30 or 15W-40 in that engine but I have still always used the straight 30W in my genset as well.

 

[sandpiper10471]

Unless you are blowing black smoke out the back end, I wouldn't mess with the timing.

 

[rardiH36]

sandpiper:

Thanks. I will leave the timing alone. No, no black smoke at all.

rardi

 

[captron]

Thanks Rich,

I'm going to stick to 30 wt. as well.

happy sailing,
Capt. Ron