Today I did my first oil change on a diesel car that I recently bought, my '91 300d. ....WHOA!! We are not in Kansas anymore, Toto!! LOTS of oil in this thing. 8 quarts, dirty and sort of thin and water-like. Changed just 3,000 miles ago by the previous owner, I guess the oil gets a good pounding from the compression of a diesel engine? A diesel just compresses the fuel, though. I was going to say from the heat of a diesel, but I've been told diesel and gas engines both run at about the same temperature, which I think was 260 degrees or something.

Why is the oil (10w40) so thin and watery, and ink black? Even small amounts of oil that I wiped up with a paper towel, were absorbed the whole way through in a second.

Editing this after reading some of the replies: Interesting reads about the oil. I'd heard if I was going to change the oil every 3k, then it really didn't matter. Being summer, 20w50 is recommended in the manual, same with 15w40, but I used the 20w50. I'll search some of the forums to see what others used on their diesels.

1991 300d, 90k

What did he put in? Maybe he had the wrong viscosity? Also the oil has soot in it. It is easy to get concrete stained with the stuff. I have tried to get it off on concrete and it isn't easy even using gasoline.

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01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

15w40 or 20w50 are better for a diesel....always use a diesel oil, so it can handle the soot levels etc....

I changed my oil today too! Mine was pretty heavy (not watery at all, despite being super hot when I changed it) and super dark though, 2,956 miles on it Shell Rotella-T 15w40 diesel oil Thats normal for a 617 though, they're soot generators.....


I changed my o-rings on my car's filter spindle again, and I think I gained back about .5 bar in pressure at hot idle....cool.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Brake cleaner and rags work pretty good, but you need a lot of it.



Another option is to rent a jackhammer, tear up said concrete...and repour. Only to be "marked" by the diesel again. So its pointless.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

There is a better option. Take enough diesel oil (Powerstroke has 15 quarts) and cover the entire driveway to match.

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01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

I agree, definatley the best idea! Then you can truly call it "diesel territory"

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Wet the spot with a hose then cover the spot with a handfull of quikdry cement, Rub it in with your foot and sweep off the excess. when it drys the spot will be gone.

One thing that I have noticed that makes a big difference between diesels and gas engines is to NOT read the oil.

On my other car, the oil would be only slightly brown after 3,000 miles. On the MB, the oil is black after about 30 miles. Just the nature of the beast. Also like stated above, use oil formulated for diesels. When I do an oil change, I come home from work (about midnight) and drain the oil and remove the filter (Yes, this stuff is hot). I let the oil drain overnight and then fill 'er up in the morning. This gets as much of the old oil out as is possible. I have considered adding a product which helps the oil clean the engine prior to draining it, but I really don't know if this is recommended.

Muriatic acid will clean the concrete but it will also eat concrete and produce poison gas. Read about how to clean the concrete without hurting it or yourself.

Yeah, I would NOT recommend any oil drain/cleaner additives to wash the inside of the engine, just use clean oil. and good filters. and remember, the oil will get filthy the instant the motor comes up to temp, cause there is about 1.5 quarts of old oil still in the cooler lines...
John

30 miles? Mine looks black after I run it for 30 seconds to put the oil through the filter!

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Ralph

1985 300D Turbo, CA model
248,650 miles and counting...

jbach36-

I do not believe that there are any diesel rated 20W-50 oils out there anymore. If you value your engine, next time it would be better to use a good 15W-40 such as Delo 400 or Delvac 1300 or a synthetic. Search and you will learn what we all use. 20W-50 was a better choice than 10W40, but diesel rated oils have additives than suspend soot better than gasser oils.

Rick

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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

You know, I did an oil change yesterday, too, and instead of using the Wix filters I've been using I used one of those made in Turkey Fram deals. The 'O' ring actually fits! I swear putting on those Wix 'O' rings is the most frustrating thing.

I also changed those little O rings on the filter housing shaft. I had to chip the other ones off, they were so hard. I doubt they've been changed in five years before yesterday.

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Ralph

1985 300D Turbo, CA model
248,650 miles and counting...

Watery thin oil also happens when the viscosity breaks down. Heat and pressure (shearing) causes that as well. While diesels do tend to run the temp as gassers, there is more pressure on the crank and rod bearings which is caused by the higher compression of a diesel. You do need a diesel specific oil which is formulated for the soot and higher pressures involved.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

I think super heavy oil is a bit of a placibo. I have never had problem's with the 5w40 I run, and my friend usualy runs 0w40 in his. Both cars have had samples sent to the lab, and the lab said couldn't look better.


You can't tell much by looks, its what the lab says thats important.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200