"Never put synthetic oil, transmission fluid, or differential fluid in it.... if you want to start having problems, just start using synthetic fluids... they loosen up stuff that shouldn't be loosened and that car wasn't designed for use with synthetic fluids."

Those were the words of my mechanic when I mentioned to him, the fact that I intend to use Amsoil synthetic fluids bumper to bumper in my 1984 300SD. I searched all over the forum and spent about 40 minutes browsing through search results and I've seen nothing but praise for Amsoil's synthetic oils and ATF. He really confused me because I had put Amsoil fluids in my 1989 Mazda 929, my 1990 Honda Civic and in my 1999 Toyota Avalon and they all run well without any issues. Additionally on the Amsoil website it is stated that the diesel oils they have a suitable for use in Mercedes-Benzes. But then again, my Mazda and my Honda have been using the fluids for over a year but I've only put on about 4,000 miles on each of them (they aren't daily drivers... just cars I bought to have for fun). I've never had any problems, or ever heard of synthetic fluids being bad for ANY car.

So right now, I am thoroughly confused and I'd greatly appreciated it if someone who has been using synthetic fluids for lots of miles spoke out to help clear my mind!!

oh man - if you only knew how we feel about oil threads.

welcome aboard

Two oils for these cars

Delvac 1 synthetic

Delo 400 dino

These are the only two oils you should consider for a diesel. I swapped my 300SD over to Delvac 1 at around 79k and I have not had any issues whatsoever with leakage or usage.

I run Delo 400 in the 300D's because I already have some leakage issues that I need to address over the next year or so.

__________________
Jim

fully synthetic in my cars and trucks and no problems..your mechanic is nuts..

__________________
2000 Ford 7.3 Powerstroke 4x4
2006 Mazda Tribute
1983 Black 300 D (donated to charity)
1993 Teal 300 D (160K) Sold
"I love the smell of burnt diesel fuel in the morning, it smells like ....VICTORY"

Semper Fidelis
USMC 1973-1976

I bought my 1983 300sd new, it came with 4 years or 48,000 miles warranty. I used it as a daily driver. A few years ago, when I could find Synthic oil at walmart for about two times the price of normal oil and my 300sd had over 100,000 miles on it, I swiched.
My 300sd is still my daily driver and has 230,000 miles on it. It get 26 to 30 mpg and has pick-up and go.
I change the oil and filter myself every 3,000 mile and it does not need any oil in that time.

When I have to use a rental or my wifes Volvo, I love the 300sd more!

I may not need to change the oil every 3,000 mile but I look forward to it.

Like what exactly?

Yeah, I've heard this before. And in hopes of avoiding an all out flame-war, I'll just say this: If you have crap stuck to parts of your engine, perhaps you aren't changing the oil frequently enough.

I forgot to say I have been using Rotrlla T Synthetic 5-40. Walmart $12 or $13 an gallon. I have not used synthetic ATF but change that my self every two years. Original engine and tran.

Many years ago detergent oil was not widely available and most just used plain old SAE 30, non-detergent. For those who switched to the new detergent oils that had already run many miles on the old non-detergent, engines began to blow up because the detergent oil statred to loosen up all the crud in the engine and clog oil passages starving bearing.

So the old adage was, never put detergent oil in an engine that had always run on non-detergent! And that still hold true today and you can still by non detergent oil.

Sounds like your mechanic is confused!

I haved used Amsoil products for over 20 years. I first started using it in my Suzuki PE250 Dirt Bike. The bike used to foul plugs like crazy. Somebody suggested using Amsoil two-stroke oil in it. I tried it and never fouled another plug. To this day I use it in chain saws, weedeaters, leafblowers etc. They all seem to start easier and run smoother. I used Amsoil in my 81 240D with 240K. It seemed to run smoother and quieter. I never had one problem with anything loosening up inside the engine. I also had a friend of mine had a Ford F-350 that wouldn't go into first gear when it was cold out. He changed the transmission fluid with Amsoil. Never had another problem getting into gear.

Andy

While we are on the Amsoil topic, I think I'm going to switch to it on my next change, it is more availible in my area. Delvac one is impossible to find. What type of Amsoil do you use in your MB? I would like to use a 15w-40 or 50 in the summer and a 5w-40 or 50 in the winter. Do they have these weights?

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Before switching an old engine to synthetic, a good cleaning is a good idea.
Check out auto rx ( www.auto-rx.com ) the stuff is costy, but it really works. I've been using it on my own cars and my customers cars for awhile now with great results every time ( I have no affiliation with them, their stuff just plain does what it says it does. I sell and install amsoil products out of my shop, but this is the cleaner that I use)I've averted a number of seal repairs with that stuff..

This is my two cents on engine flushing. Before I do it on a Mercedes diesel I drop the oil pan and clean up any sludge. I then paint the inside of the oil pan with either Glyptal (available from Eastwood) or POR-15. I then reinstall it and of course replace the oil. At the next time it is due for an oil change I flush the engine. If you have a lot of sludge in your oil pan an engine flush can cause too much debris to go to your filter which in turn clogs it. Then you have that extremely filthy oil which is not filtered circulating. By painting the inside of the oil pan the surface becomes too slick for deposits to form causing it to be picked up by your filter. Just be careful during future oil changes cause it really shoots out when you remove the drain plug. By the way Amsoil is available online with direct shipping to your door.


Andy

is it really necessary to have synthetic oil ? i change the oil every 3k miles religiously (filter also)..... isn't that enough ?

i use Rotella 15-40

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Audi TT

I've had similar results with Seafoam, although admittedly I haven't taken an engine apart yet that I've used SeaFoam on (operative word: "yet"...my truck's engine's partially coming apart soon and I'll see the rearl results). You can get a can of Seafoam for about $6 at Napa Auto Parts. I add one pint into the oil a few hundred miles before I plan to change the oil.

With the truck, after treating the oil like this twice or three times, the oil would actually look clean after almost 3000 miles of use. I was shocked the first time I saw it as well, but it seems to really work. But, time will tell for sure when the engine comes apart (doing head gaskets and lifters)...hopefully within the week.

BTW, on the synthetic issue, I'm one of the people who's scared by the theory of seals swelling up with new oil and developing leaks where there were none before. This is the only thing stopping me from using synthetic in my engines, and I am already using synthetic in the Benz's differential and in the truck's tranny and transfer case (and when I do a differential oil change on the truck, or a tranny oil change on the car, I plan to go to synthetic). Synthetic's more refined than dino oil, and I also like the idea of not depending on petroleum oil resources any more than absolutely necessary (and am looking into a WVO conversion for the same reason). When I put my truck back together, the only seals/gaskets that won't be replaced will be the rear main seal and the oil pan gasket, so I may try synthetic in the truck and see how she does...

__________________
2001 VW Jetta TDI, 5 speed, daily driver
1991 Ford F-350, work in progress
1984 Ford F-250 4x4, 6.9l turbo diesel, 5 speed manual
Previous oilburners: 1980 IH Scout, 1984 E-350, 1985 M-B 300D, 1979 M-B 300SD, 1983 M-B 300D
Spark-free since 1999

FWIW, switched both cars over to Mobil's Delvac 1 5W-40 after purchase.
The 617 in the '82 300D had 112K when purchased; no leaks or reported consumption. 30K later, no leaks or consumption between 5K oil changes.
The 602 in the '93 2.5 Turbo had 143K when purchased; no leaks or reported consumption. 25K later and it too remains leak free and does not consume oil between 5K changes.
Summary: synthetic or dino, if the car had pre-exisiting leaks or consumption problems I would look further than the oil selected.
As for oil brand, I'll stick with the majors; ExxonMobil has a demonstrated legacy with synthetic oil technology. Much of the research that went into developing their Mobil 1 line of synthetic motor oils probably helped in the development of Delvac 1.
Just my thoughts on the subject.

__________________
'82 300D Turbo 204K
'10 Toyota Prius 85K
'13 AMG C63 (P30) 23K
'14 Audi Q5 TDI 46K
'16 RAM 2500 CTD 12K

'10 VW Jetta TDI 65K (traded)
'12 Nissan Leaf 34K (returned end of lease)
'15 Audi A6 TDI 25K (traded)
'95 E320 166K (traded)
'93 300D 2.5 Turbo 168K (sold)

Oh I know... as I was doing my research by checking out search results, I saw several threads in which the first reply was something like "not another oil thread"! Couldn't resist joining the party though.

Like AndyRM said, Amsoil is available on the web with direct shipping right to your door. I'd like to use either the 10W-40 multigrade oil or the 15W-40 Heavy Duty Oil for Diesel engines. They don't have 5W-40 or 50 though. Just check out this page to see all the Amsoil synthetic motor oils you can get.


Thank you all for your responses. I have been really confused about this. I have a friend with a 1981 Toyota 2.2L Diesel pickup truck and he has been running Amsoil for 19K miles. I was wondering why an old Toyota can run it bumper to bumper with no issues, yet a so-called "super engineered" benz can't. And yet the mechanic that got me all confused has been working on Benzes and Bimmers (the latter mostly though) for 16 years!

So the general solution is as follows: use a good engine flush to clean out any crud in the engine first, then apply synthetic oil.