Oil Residue Question

[maduell]

Since I was replacing plugs, wires, coils, vac tubing, breather hoses, etc. I thought it would be a good time to follow Gerry's great tutorial on replacing head cover gaskets and cam chain guides. Now I am wondering what may be going on inside my engine to cause the "varnish" look. Although I was not really concerned at first because there is no sludge apparent, and everything looks well lubricated and in good order.... now I am envious of the cleanliness inside his engine and want mine to look like that too. (I know, would probably have to tear the engine down)

mine looks like this:

and his looked like this: (mileage?)

my head covers (started to clean the left bank):

and his (pre clean):

I have been running Mobil1 5-30 since I took over maintenance around 60k miles (now 111k) and always use MB filters...no additives. Regular oil/filter changes 4-5k. Mileage is pretty much short runs and wondering if that makes a big difference...? Cleanup of covers is a big task but what should I do, if anything about the "varnish" apparent in this engine?

*note: I already had the metal oil tubes but replaced the cam chain guides.

PLEASE no rants or sales/marketing discussions about oil! If it is good enough for racing engines I thought my "driver" should be fine with Mobil1...or should it?

 

[samiam44]

I would try an ester based oil. Redline or motul.

Nothing to worry about.

 

[gerryvz]

My mileage on that would have been around 115-120K at that time. My car currently has 129K on it.

I used Mobil 1 from the day I first got the car, and several years ago switched over to RedLine (15W-50?) oil, per advice of GSXR. I have ALWAYS changed my oil in the E500 (always synthetic) at 5K intervals. Before using the RedLine, I used the Mobil 1 TDT (Turbo-Diesel Truck) oil, and I believe that most diesel-rated oils tend to have higher levels of detergents in them than strictly gas-engine-rated oils. I am sure that the detergents kept the inside of things clean.

Same thing with the M104 engine, on my former E320 wagon. I for some years have used dino-oil on that, but it has been the Chevron DELO 400 LE (15W-40) oil for diesels, and it also has high levels of detergents that keep things clean. That oil was always changed at 2,000-3,000 mile intervals. I continue to use that oil in my G320, which has the 104.996 variant of that engine.

(Which reminds me, I need to change the G's oil today!! It's got 2,300 miles on it).

Usually I only have seen that kind of varnish with engines that have used dino oil, and probably oil that was extended out to the factory-specified 7,500-mile change intervals. So it could well be that the car had extended drains of dino oil before you got it.

I think I would recommend going over to a full-synthetic oil (perhaps RedLine) or something with a bit more detergent content for the next few oil changes, and change it at a 3K-ish interval to see if you can clear out some of that varnish.

What I would NOT do is add any type of SeaFoam or other additive. Just let detergents in the oil do their work over time.

Cheers,
Gerry

 

[gerryvz]

Also, I think your short-run mileage has A LOT if not EVERYTHING to do with the varnish, not the oil itself. If you're always doing short runs, then your oil never gets hot enough to "cook off" the contaminants and combustion by-products, and can't get things heated up enough to use the detergents in the oil to remove the baked on varnish.

The solution, in addition to using more detergent oil, is simply to drive the car on longer trips (15+ miles minimum) to get the oil heated up enough so that it does what it is supposed to do.

Cheers,
Gerry

 

[Glen]

Also, I think your short-run mileage has A LOT if not EVERYTHING to do with the varnish, not the oil itself. If you're always doing short runs, then your oil never gets hot enough to "cook off" the contaminants and combustion by-products, and can't get things heated up enough to use the detergents in the oil to remove the baked on varnish.

The solution, in addition to using more detergent oil, is simply to drive the car on longer trips (15+ miles minimum) to get the oil heated up enough so that it does what it is supposed to do.

Cheers,
Gerry

^This.

 

[gsxr]

Usually I only have seen that kind of varnish with engines that have used dino oil, and probably oil that was extended out to the factory-specified 7,500-mile change intervals. So it could well be that the car had extended drains of dino oil before you got it.

Ditto what Gerry said. The varnish is likely from the 60kmi before you purchased the car. It won't hurt anything, don't lose sleep over it. The important part is that you do not have sludge.

I think I would recommend going over to a full-synthetic oil (perhaps RedLine) or something with a bit more detergent content for the next few oil changes, and change it at a 3K-ish interval to see if you can clear out some of that varnish.

I believe ester-based oils (i.e., Red Line) may have a bit more cleaning properties, but it will take quite a long time (like, another 25-50kmi before you'd see much change... if any.

What I would NOT do is add any type of SeaFoam or other additive. Just let detergents in the oil do their work over time.

Absolutely correct. DO NOT use additives.

I have been running Mobil-1 5-30 since I took over maintenance around 60k miles (now 111k) and always use MB filters...no additives. Regular oil/filter changes 4-5k. Mileage is pretty much short runs and wondering if that makes a big difference...? Cleanup of covers is a big task but what should I do, if anything about the "varnish" apparent in this engine? PLEASE no rants or sales/marketing discussions about oil! If it is good enough for racing engines I thought my "driver" should be fine with Mobil1...or should it?

Mobil-1 is not bad oil, but most of their lineup in USA is no longer a true synthetic, except for the "Extended Performance" brand. The rest is a Group III hydrocracked dino oil that Mobil markets as "synthetic". Extended drain intervals are safe with the "EP" version, otherwise the normal M-1 should be changed like it was dino oil (i.e., 3-5kmi depending on normal vs severe service). If most of your driving is short trips... you should be changing at 3kmi, not 4-5k (unless you are using EP, in which case 5k is fine).

However: Mercedes does not recommend 5W-30 for the M119 engine in warm climates (>86°F ambient). The recommended viscosity in the owner's manual is xW-40 or xW-50, see attached PDF file. I personally use 10W-40 in all my cars. When using synthetics, you don't need anything thinner unless you occasionally see polar bears in your back yard. There is, IMNSHO, no significant advantage to the thin stuff.

 

[Klink]

Since I was replacing plugs, wires, coils, vac tubing, breather hoses, etc. I thought it would be a good time to follow Gerry's great tutorial on replacing head cover gaskets and cam chain guides. Now I am wondering what may be going on inside my engine to cause the "varnish" look. Although I was not really concerned at first because there is no sludge apparent, and everything looks well lubricated and in good order.... now I am envious of the cleanliness inside his engine and want mine to look like that too. (I know, would probably have to tear the engine down)

I have been running Mobil1 5-30 since I took over maintenance around 60k miles (now 111k) and always use MB filters...no additives. Regular oil/filter changes 4-5k. Mileage is pretty much short runs and wondering if that makes a big difference...? Cleanup of covers is a big task but what should I do, if anything about the "varnish" apparent in this engine?

PLEASE no rants or sales/marketing discussions about oil! If it is good enough for racing engines I thought my "driver" should be fine with Mobil1...or should it?

Note! These are M119 specific comments!

That is just some surface varnish from the engines early days on Dino. Do not worry about it one bit, and do not do anything to try to "clean" it. If there was any sludge in there, your ownership, the Mobil 1, and your propensity towards performing oil changes in good time has gotten it out of there.

Your point is well taken, and your instincts are spot on that "oil brand/type" fetishism is useless. I would only insist that it meets the correct MB specific specs, which in your case is MB229.3 and/or MB229.5.

My only comments regarding your oil choice are these: if you like Mobil 1 (I'm fine with it) and want to continue to run it, why don't you use the one of the versions that were literally designed with your engine in mind?

The most readily available is the 0W – 40 "European formula" You can find that just about any place that sells oil.

Many Benz dealers sell a 5W-40 version of that exact oil called "Formula M" There is also a 0W–40 version of "formula M" and I have not the slightest doubt that it is identical to the "European formula" 0W-40 that you can buy at any parts store. Most dealers that use it stock the 5W–40 version because it's a little cheaper, and yes there is a faction of people out there that just gets goofy when they see the "0" You can guess what the "M" stands for, and it has nothing to do with any BMW, though I'm sure it would work fine in those also if they use the same viscosity.
Do not confuse this with the "Formula M/ESP" that the dealers or your parts store may also have!!
That is a diesel biased oil formulated to protect the particulate filters and other claptrap that line the diesel exhaust system these days. The "ESP" in the designation is "emission system protection" in case anyone had to know.

If you have a viscosity fetish, and you just can't stand to see a "0" in your viscosity rating, Benz and Porsche dealers also sell a Mobil 1 chemically identical to the "European Formula" and the "Formula M" except that it is a 5W–50. If you wondered, it is approved for some hot rod Porsche, and the MB/McLaren SLR. You can probably find it on the Internet somewhere for a reasonable price if you think that would be your thing.

Now, here is an outlier that I have had great success with:
Most of these engines are old and a little seepy, if not downright drippy, and it is not uncommon that upon conversion to some of these water thin synthetics, they can start to pour oil from everywhere. Some call this observation a "wives tale" but in the immortal words of Tommy Boy, "I've seen it 100 times" Others may say "well that's just proof that your engine needed [to be] resealed anyway" which is true, but just maybe you didn't feel like having to completely reseal your engine exactly now today.

That leads me to mention this oil, also available pretty much everywhere, including Walmart for dirt cheap. It is Mobil 1 "High Mileage" It is available in a 10w-40, and I have it on good confidence, and the specification sheets tended to bear out that it is basically identical to the oils I just discussed above with a tiny smidge of extra seal conditioner in it.
I have put it in many older and MBs and not experienced the usual resulting tribute to Capt. Hazelwood...

Any one of these oils, changed at the recommended time/mileage interval will give you perfect protection against anything that oil is capable of protecting you from.

Do I think you are hurting anything by using the 5W–30 if you have some kind of particular affection for it? No. I am only splitting the two halves of the previously split hair. Now to split one of those quarter hairs, the last time I looked, all of their 5W-30s, except possibly the "high mileage" version were ultra low zinc/phosphorus formulations intended mostly for use in newer engines that have almost universally adopted roller tappets for US CAFE/ECE carbon emission limits. Many argue that this has no relevance to an enthusiast car that sees frequent oil changes, and that may be correct, but it still gives me a tiny twinge of the willies. Less with this motor than with some even older designs, but still the willies.

I hope that I have not done here exactly what you were hoping to avoid. If I have, my apology is offered...

 

[maw1124]

I had been thinking about this for the Audi 4.2 engine, which is notorious for oil consumption (ring blow by), but the heavier weight synthetics (10w50, 15w40) tend to be turbo diesel marketed applications and I didn't know the difference or applicability to naturally aspirated high compression cars. (I know what I know, I don't know what I don't know -- sue me). I've suspected Audi jus spec'd it too thin in the Allroad, expecting it to see "polar bear" use (thanks GSXR) most of the time. Indeed, my kids use to call it The Ice Bear, since that's what it acts like. So thanks GVZ and Klink for clearing that up, and thanks maduell for bringing it up.

Cheers,

maw

 

[Klink]

I had been thinking about this for the Audi 4.2 engine, which is notorious for oil consumption (ring blow by), but the heavier weight synthetics (10w50, 15w40) tend to be turbo diesel marketed applications and I didn't know the difference or applicability to naturally aspirated high compression cars. (I know what I know, I don't know what I don't know -- sue me). I've suspected Audi jus spec'd it too thin in the Allroad, expecting it to see "polar bear" use (thanks GSXR) most of the time. Indeed, my kids use to call it The Ice Bear, since that's what it acts like. So thanks GVZ and Klink for clearing that up, and thanks maduell for bringing it up.

Cheers,

maw

And, if you think a higher hot viscosity may be your cure and you don't want to risk your catalyst with some "racing" type of oil having a bunch of zinc/phosphorus, there is always the Castrol 10 W–60 originally suggested to help keep the notoriously fragile last version M3 in-line six from destroying itself
There is also the LubroMoly 10-60 purpose formulated for exactly the same application. Both are widely available on the Internet, I even see the LubroMoly at a local NAPA.

 

[Trae]

Hi Klink,

At one point, I was running Redline 15-50.

Pretty thick stuff.

 

[Klink]

Hi Klink,

At one point, I was running Redline 15-50.

Pretty thick stuff.

Like my head, Trae. Just like my head

 

[clarkz71]

.
.
Redline is good, however Motul is actually MB approved.

 

[Glen]

Note! These are M119 specific comments!

That is just some surface varnish from the engines early days on Dino. Do not worry about it one bit, and do not do anything to try to "clean" it. If there was any sludge in there, your ownership, the Mobil 1, and your propensity towards performing oil changes in good time has gotten it out of there.

Your point is well taken, and your instincts are spot on that "oil brand/type" fetishism is useless. I would only insist that it meets the correct MB specific specs, which in your case is MB229.3 and/or MB229.5.

My only comments regarding your oil choice are these: if you like Mobil 1 (I'm fine with it) and want to continue to run it, why don't you use the one of the versions that were literally designed with your engine in mind?

The most readily available is the 0W – 40 "European formula" You can find that just about any place that sells oil.

Many Benz dealers sell a 5W-40 version of that exact oil called "Formula M" There is also a 0W–40 version of "formula M" and I have not the slightest doubt that it is identical to the "European formula" 0W-40 that you can buy at any parts store. Most dealers that use it stock the 5W–40 version because it's a little cheaper, and yes there is a faction of people out there that just gets goofy when they see the "0" You can guess what the "M" stands for, and it has nothing to do with any BMW, though I'm sure it would work fine in those also if they use the same viscosity.
Do not confuse this with the "Formula M/ESP" that the dealers or your parts store may also have!!
That is a diesel biased oil formulated to protect the particulate filters and other claptrap that line the diesel exhaust system these days. The "ESP" in the designation is "emission system protection" in case anyone had to know.

If you have a viscosity fetish, and you just can't stand to see a "0" in your viscosity rating, Benz and Porsche dealers also sell a Mobil 1 chemically identical to the "European Formula" and the "Formula M" except that it is a 5W–50. If you wondered, it is approved for some hot rod Porsche, and the MB/McLaren SLR. You can probably find it on the Internet somewhere for a reasonable price if you think that would be your thing.

Now, here is an outlier that I have had great success with:
Most of these engines are old and a little seepy, if not downright drippy, and it is not uncommon that upon conversion to some of these water thin synthetics, they can start to pour oil from everywhere. Some call this observation a "wives tale" but in the immortal words of Tommy Boy, "I've seen it 100 times" Others may say "well that's just proof that your engine needed [to be] resealed anyway" which is true, but just maybe you didn't feel like having to completely reseal your engine exactly now today.

That leads me to mention this oil, also available pretty much everywhere, including Walmart for dirt cheap. It is Mobil 1 "High Mileage" It is available in a 10w-40, and I have it on good confidence, and the specification sheets tended to bear out that it is basically identical to the oils I just discussed above with a tiny smidge of extra seal conditioner in it.
I have put it in many older and MBs and not experienced the usual resulting tribute to Capt. Hazelwood...

Any one of these oils, changed at the recommended time/mileage interval will give you perfect protection against anything that oil is capable of protecting you from.

Do I think you are hurting anything by using the 5W–30 if you have some kind of particular affection for it? No. I am only splitting the two halves of the previously split hair. Now to split one of those quarter hairs, the last time I looked, all of their 5W-30s, except possibly the "high mileage" version were ultra low zinc/phosphorus formulations intended mostly for use in newer engines that have almost universally adopted roller tappets for US CAFE/ECE carbon emission limits. Many argue that this has no relevance to an enthusiast car that sees frequent oil changes, and that may be correct, but it still gives me a tiny twinge of the willies. Less with this motor than with some even older designs, but still the willies.

I hope that I have not done here exactly what you were hoping to avoid. If I have, my apology is offered...

Klink, I know this is all opinion on your part but it sure makes sense...maybe because it matches my own exactly! Thanks

 

[maduell]

OK...I have decided on the oil, thank you all!!

Next... one side had this attached to an apparent breather tube on the cover...

here is the other side...was nothing there when I removed...

this appears to have been a breather hose...and looks to be broken off on the end that faced the block/head under spark plug hole...

 

[maduell]

after closer inspection of mine and Gerry's...his does not appear to have the same cover...? Here is my engine number:
11997512 006874

Maybe I have a different version and ventilation setup...?

 

[clarkz71]

Part#'s for the [oil separator] breather pictured

119-016-01-81 - Rubber funnel [$22 list, April 2024]
119-010-00-62 - Plastic bracket [$7 list, April 2024]

Only on one side [passenger side cylinder head].

 

[clarkz71]

As you can see in gsxr's image, it is installed under the #4 spark plug
It is pressed into the head.

 

[gsxr]

Remember to fish out the old/broken plastic piece from the head before you install the new parts. I bet you'll be surprised at how soft the new "funnel" is, compared to the fossilized old one.

 

[maduell]

uggggh...how do I remove without getting "fossilized" pieces everywhere...it is all very brittle now.

and my parts box is already to come home...I will look local for this one.

 

[maduell]

Part#'s for the breather pictured

119 010 00 62
119-016 01 81

Only on one side.

I could not find this on EPC...thanks! Now I see it though Oil Separator and Molded Hose...hahaha!

 

[gerryvz]

I've always been a fan of a bit heavier oils. It seems that when our cars were new, and during that era, that heavier oils were more "in vogue" but my perception may be wrong on that count.

I have used 20W-50 oil in my 560SEC since I bought it 12.5 years ago, with no issues, even in that cold(er) climate than Houston. For years I used the Chevron Supreme version, until my top-end job nearly 5 years ago, when I began using the Brad Penn 20W-50. For my M104(s) I've used 15W-40, and in the E500 I've mainly used 15W-40 and 15W-50 oils. Though for a time, many years ago, I did use the Mobil 1 "European Formula" 0W-50 oil probably for a couple of oil changes, with no problem.

I never noticed any "butt dyno" results in terms of power and torque generation between the various oils and weights I've used.

Also, some time back I changed the transfer case and front/rear differential oils on my G-wagen and replaced them with RedLine fully synthetic gear oils. I have NOT seen even a single drop leak from either diff, or from the critical transfer case of the G. Nor from the rear diff of my 560SEC, which also received the synthetic RedLine diff juice.

 

[gerryvz]

I could not find this on EPC...thanks!

If you use my "parts search" portion of my EPC 101 lesson, you should be able to type in the part numbers and then see all applications for that particular number. When you click on your engine or model, then it should take you to the diagram where it's used.

 

[clarkz71]

This is more then likely easier.

 

[samiam44]

I use a dash puller hook and it came out easily.

M

 

[gerryvz]

I use a dash puller hook and it came out easily.

M

 

[maduell]

.
.
Redline is good, however Motul is actually MB approved.

Pick up two fivers today...$90.00 ($9.00/Ltr)

 

[clarkz71]

That's a good price.

Cost is $35 per jug if you're a shop.

I buy 6 at a time, just in case the price goes up.

 

[maduell]

I pulled the old oil separator piece out with a small pick and a portion of the barb was left in...when I tried to get that small piece out it seems to have disappeared. If it went down into the engine where it sits, do I need to worry? Or will it end up in the oil pan?

Above is with the separator still in...below is after I got it out and lost sight of that smaller barb piece. The left hole (smaller one) held on to the barb that is seen as missing.

My initial thought is NO PROBLEM, since it is plastic, and fairly small...BUT, I hope no oil passage gets blocked somehow...am I being paranoid?

How do I get it to press/seat in the hole? I can't seem to get it to "snap" in.

 

[maw1124]

And, if you think a higher hot viscosity may be your cure and you don't want to risk your catalyst with some "racing" type of oil having a bunch of zinc/phosphorus, there is always the Castrol 10 W–60 originally suggested to help keep the notoriously fragile last version M3 in-line six from destroying itself
There is also the LubroMoly 10-60 purpose formulated for exactly the same application. Both are widely available on the Internet, I even see the LubroMoly at a local NAPA.

That's certainly part of my thought process, as I look at the engine comparisons -- two naturally aspirated motors with roughly the same compression (11.5 to 1 in the M3, 11 to 1 in the Allroad 4.2, both higher than the 500E). The Allroad 4.2 specs 5w40, and I'm moving to race cats anyway (the car has over 170k on the clock and the originals are done).

I've been thinking to move to 10w40 or 10w50. If it was in FL, I'd go 10w50, which the guys used to put in my 500E. It's all a bit of a science project (looking for perfection in an imperfect world), since the car sees less than 10k a year. But it's all about the learning anyway. So thanks for your help Gents.

Cheers,

maw

 

[DerFuror]

Re: Busted Barb

I pulled the old oil separator piece out with a small pick and a portion of the barb was left in...when I tried to get that small piece out it seems to have disappeared. If it went down into the engine where it sits, do I need to worry? Or will it end up in the oil pan?

Not much you can do about it. Most crap will eventually end up in the pan. Strainer & filter will keep it from recirculating. Low probability of permanently lodging in a passage. The remnants will continue to disintegrate under environmental factors until they flush to the pan.

How do I get it to press/seat in the hole? I can't seem to get it to "snap" in.

- Lube the hole up nicely with heavy oil or Vaseline
- Carefully warm-up the barb with hot air gun (low setting).
- Line-up part with holes. Press home using a wooden dowel (or small hammer handle end) that mates squarely & firmly with part.

 

[Klink]

Re: Busted Barb

Klink, behave...

 

[samiam44]

Re: Busted Barb

not to worry- it is on the non-pressurized part of the oil system.

Plastic should return to the pan.

Michael

 

[jonie13]

Man, I had the exact same issue with the oil separator. I used the pick method along with a long wood screw to carefully pull mine out after it broke. Probably have a few very small pieces of plastic left in the head...which I will look for when I replace the gasket on my lower oil pan. The biggest pain I had was with trying to get the new piece back in. I used assembly lube and a heat gun (as mentioned) to try to get it to snap in. Eventually got it to click in...at least I think. All I know is that I couldn't get it back out! My hope is that it won't somehow come lose if I didn't get it to go all the way in there. My thought it that it will be somewhat held into place by the rubber tube and metal breather tube inserted into it...and the crazy amount of force I was applying!

 

[alabbasi]

I use 0w40 in my E55 but found that the M119 engine sounds like a bag of nails clattering around on anything thinner then 15w50 so this is what I stick with. Regular oil changes with a high detergent oil like diesel engine oils will clean the engine slowly.

I just bought a new cheap E55 and this is what I pulled out when I changed the oil. I'll be doing another oil change in about 2000 miles as the fresh oil turned black the moment I cranked the engine.

 

[Sarkisv]

I use 0w40 in my E55 but found that the M119 engine sounds like a bag of nails clattering around on anything thinner then 15w50 so this is what I stick with. Regular oil changes with a high detergent oil like diesel engine oils will clean the engine slowly.

I just bought a new cheap E55 and this is what I pulled out when I changed the oil. I'll be doing another oil change in about 2000 miles as the fresh oil turned black the moment I cranked the engine.

What brand 15W-50 motor oil do you use in your M119?

 

[alabbasi]

Mobil 1. It's available at Walmart in 5QT Jugs for under $30

 

[Sarkisv]

I use 0w40 in my E55 but found that the M119 engine sounds like a bag of nails clattering around on anything thinner then 15w50 so this is what I stick with. Regular oil changes with a high detergent oil like diesel engine oils will clean the engine slowly.

I just bought a new cheap E55 and this is what I pulled out when I changed the oil. I'll be doing another oil change in about 2000 miles as the fresh oil turned black the moment I cranked the

 

[Sarkisv]

Do you use diesel oil in between every oil change? Which brand diesel oil are you using and how long do you leave it in the M119?

 

[gsxr]

The diesel oil high-detergent thing is slowly becoming more of a myth than fact. Diesels oils may have (slightly) higher levels of ZDDP but may not have any more "cleaning" capability vs non-diesel oil. ZDDP isn't a concern for Mercedes DOHC engines.

Fact: Oil formulations keep changing / evolving over time, as API and other industry specifications change. What was true 10, 20, 30 years ago is likely NOT still accurate with most of the oils on the shelf today, especially "mainstream" brand oils (Mobil-1, Castrol, Pennzoil, Valvoline, etc). The "boutique" oils are a different ballgame though (Red Line, Amsoil, Royal Purple, Motul) but you will pay dearly for those.

Anyone interested in this stuff should watch some of Lake Speed's videos. This guy knows his stuff and backs it up with real data.

The Motor Oil Geek

As a Certified Lubrication Specialist with over 20 years experience, The Motor Oil Geek channel delivers real data about motor oils from an expert perspective instead of speculation. Twice each month I will upload a new video that either analyzes a new oil, dyno tests an oil, reveals the details...

www.youtube.com

 

[gerryvz]

The diesel oil high-detergent thing is slowly becoming more of a myth than fact. Diesels oils may have (slightly) higher levels of ZDDP but may not have any more "cleaning" capability vs non-diesel oil.

I have always understood it that Diesel-specific oils have always had a bit more detergent additives (in addition to ZDDP) to help combat diesel soot on the inside of the engine.

 

[alabbasi]

Do you use diesel oil in between every oil change? Which brand diesel oil are you using and how long do you leave it in the M119?

I have not used diesel oil in an M119, it seems to do very well with synthetic 15w50.