I'm about to change the engine oil in my 1985 300SD, can I or should I use motor flush?

Ahhhhh NO!!!!! Motor Flush is nothing more than kerosine. What ever gunk it doesn't break free, it will loosen. Then when you go to drive off, at some point that loosened gunk will become lodged somewhere you don't want it to. What makes you think you need to go to this extreme. Look inside your oil cap and see if there is any build up.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
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I have used motor flush with what i believe to be great success. the post preceeding mine has its merits, but motor flush can be used if the history of the motor is known and it has had regular oil changes. i just used motor flush in my 85 300dt with 150k and after i drained the oil with the flush in it, i filled it with some 5-30, ran it for 10 minutes at 1500 rpm, then drained and changed the filter, and added 5-40 synthetic rotella. i believe that if you flush the motor immediately after with straight oil then using flush on a well maintained motor can only help. i know, as do 2 bystanders, that my car sounded smoother after i was done. now the question is, was it because of hte motor flush or because of the synthetic oil? i've used flush every 12k and have had good success on numerous motors, to include 2 nissan maxima diesels that i had back in college. i got over 200k out of both of those motors with good compression and easy starts down to 5 degrees f upstate new york. i sold both of those cars in good running order and never did any internal motor repairs. motor flush is good in my opinion if used right.

Diesel engines do not generally accumulate much sludge and varnish as do gas engines. There is normally no reason to flush the engine with a solvent. If you really want to clean it up a bit, just do a couple 50 mile oil changes.

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Palangi

2004 C240 Wagon 203.261 Baby Benz
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To add to the excellent 50 mile oil change recommendation I suggest:

Use a universal grade oil which has more detergent additives to deal with soot dispersal, these are formulated especially for diesels. Examples are: Chevron Delo Multigrade, Mobil Delvac, Mobil Delvac One and Shell Rotella T.

Ensure that the oil is at operating temperature(minimum of about 17 miles driving) when you pull the drain plug. This will ensure that the sludge is churned up in the oil so it will come out, and it will be thinner allowing more oil to come out.

Drain overnight if possible, this will get every last bit of sludge out that can come out.

Good luck,

I use a flush each time I change the oil. I figure it helps clean some of the crud out of the engine and that is the purpose of an oil change. You put detergent in your wash machine don't you?

If you pour the flush on a dirty grease spot, you can see how it disperses the dirt in the spot which just pouring oil on the spot wouldn't do. This proves to me that the flush helps clean the internal parts of the engine.

I realize that this is an individual preference so some do and some don't. Everybody has their own procedures.

P E H

I certainly don't agree with a 50 mile oil change. What a waste of oil and money when a can of flush will do the same or more. I use synthetic oil and it would be cost prohibitive to throw away oil after 50 miles when it is made to go 10,000 miles or more.

P E H

Oil is VERY cheap relative to a Benz diesel engine. The problem with the flush approach is the lack of lubricity while the flush is circulating. If you don't load the motor while it is in the crankcase, you can probably get by with it. The main thing is that you don't drive it with the flush in the crankcase.

Good luck,

Larry,

I agree with you about not driving the car when the flush is in it. I just fast idle about 10 minutes like it says in the flush instructions.

P E H

Thank you Guys

If engine flush is basically just kerosene, is there any chance that the engine could "run away" and start sucking up the flush/kerosene & then motor oil, causing all sorts of mechanical damage? What a horrible thought.

Ducati:

No possibility. The only place the engine could "SUCK UP" the flush would be past rings or thru the valve guides. If they are that bad that the engine could get enough oil and flush by them to run away, I doubt the enging would run in the first place.

Remember one quart of flush is mixed with 7 quarts of oil and its not that much lower viscosity then the undiluted engine oil. Also its not kerosene, its more like dry cleaning fluid. Its a myth that kerosene is a good cleaner, gasoline yes , kerosene no. Kerosene is oil, just a little lower viscosity than #2 fuel or Diesel oil.

BTW, I installed Evans waterless coolant in my '87 300SDL but it went away for winter storage before I got a chance to test it. Actually it won't get a real test until I take it to Death Valley or some hot place like that. When I do, I will make a report.

P E H

I appreciate the input. As I want a clean engine (if that is even possible with a diesel) I will use engine flush as per the instructions. Regarding Evans Waterless, I should ask if this can cause an engine to run too cool? I understand that there is an optimal temperature that diesels run best at. It can get hot here in the summer, but I sure do not need additional cooling in the winter. Evans causes faster warmups, I understand.

The 50 mile oil change is a good idea!

That should do a fine job of getting all the old worn out oil out of there, but I don't see the point of it all with a diesel...

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Ed
1981 300CD (Benzina)
1968 250 S (Gina) 266,000 miles!
1983 Alfa Romeo GTV6 (Guido)
1976 Jaguar XJS-saved a V-12 from the chevy curse, what a great engine!
1988 Cadillac Eldorado (better car than you might think!)
1988 Yamaha Venture (better than a Wing!)
1977 Suzuki GS750B
1976 Yamaha XS 650 (sold)
1991 Suzuki GSX1100G (Shafty Gixser)
1981 Yamaha VX920RH (Euro "Virago")
Solex Moped
1975 Dodge P/U camper


"Time spent in the company of a cat, a beer, and this forum, is not time wasted!"

Regardless of how much and how often you flush a diesel crankcase it will usually still have black oil on the dipstick. A fresh engine that has no significant blowby will be your only chance of brown oil on the dipstick.

My daughter's car now has about 7,000 miles on the rebuild, and still has oil that is not black on the dipstick for as long as 1,000 miles or so after one of my hot, overnight oil drains.

In my experience, there are very few diesel engines that will remain in such condition for very long.

Good luck and keep on changin' that oil,