I recently got a letter from MBUSA stating that you should use synthetic oil in the ML320. That makes sense, because with the Flexible Service Interval feature you can go up to 18,000 miles between oil changes. However, I have also seen claims that you should use synthetic in a diesel also. This would seem to be awfully expensive; due to loading with soot particles, you have to change the oil in a diesel every 3500 miles or so, no matter what kind of oil it is. I'd think the benefit of the synthetic oil would be negated by the extreme added cost (unless you have a special case like very low temperature operation). Does anybody have an informed opinion on this?

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Bill
- 1991 300D Turbo 2.5
- 2000 ML 320

Go for it. Delvac 1, which is the diesel version of Mobil 1 is one of the best oils you will find for use in a diesel vehicle. It has an API rating of CH-4 and is great at controlling soot. You should be able to double your change intervals and the synthetic will also give you the added benefit of helping your turbo run cooler.

The Delvac 1 only comes in 5W40, but that is not all bad because you can run in it in warm and cold climates as well. I think you would be very pleased by changing over to the synthetic, especially if you plan on keeping your car for an extended period of time. If you do change over I would highly recommend at least changing your filter at 1500 miles, if not both filter and oil. The synthetic will help clean out some of the gunk in your engine and the filter will get loaded up fairly quickly. Johnny

I don't know if it makes sense or not, but per "FACTORY APPROVED SERVICE PRODUCTS", Section B for S3 engines, synth oils are not listed.
New AMG Benzs come with Mobile 1 all others in my part of the USA have 20-50w oil.
You have opened a can of worms and just wait for all of the suportive and negative data that will follow.
Happy Trails Beep Beep from Houston!!!
Don, El Cheapo

Oh boy here we go again.

Hello Donald, nice to see u back in action.

BTW, this is currently a hot topic in MBCA.org

Yes, its safe and good to use synthetic in diesels, all 3 of mine use it, Mobil 1 15w-50. But change the oil every 4,000 miles maximum. This is partially due to the soot. Its not a good idea to not change the oil in any car for 18,000 miles. Yes it is way more expensive than conventional oil, but I change the oil myself, so I save on labor costs and apply it to better quality oil. Besides its cheaper for better oil changes than a new engine.

Most people would agree synthetic oil is superior to dino juice. I think it is really a question of being cost effective and that depends on the individual. I run synthetic in my ML and change it at 7500 miles. On the other hand, I run Shell Rotella in the E300 and change it every 5000 miles. Why the difference? The way the cars are driven is why. I drive the E300 about 2000 miles a month and my wife drives the ML about 500-600 miles a month. That oil stays in the E300 about 3 months and in the ML for about a year. I chose to go synthetic due to the time interval between changes in the ML.

As far as testimonials with diesels, what do the truckers use? They might be a good source of info.

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99 E300 133K
98 ML320 99K
87 Saab 900 Turbo Conv 123K

The reason to use synthetic engine oil is engine and engine component longevity ... the minor improvements in a variety of characteristics like mileage, don't pass the logic test due to the cost delta of the synthetic engine oils. The one exception to this is extremely cold climates - synthetics flow so much better that you can actually START the engines - and, have added benefit, again, of the oil getting to the parts that need it - increasing longevity of parts and the engine.

The cost versus effects curves look different for things like differentials, greasable fits and bearings, and even transmissions, due to the change interval.

George

If you go to the Mobil website, for over-the-road truckers running Delvac 1 they recommend a VERY long change interval, something like 100k miles or more. That led me to believe that the Delvac1 can carry a LOT of soot.

I run Delvac 1 in my Diesel, and it started incredibly easy during some really cold temps...starts better than my gas motors!

My plan is to change the oil every 7,500-10,000 mi, whether it needs it or not.

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"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo

As regards the recent letter from MBUSA, it is specifically referring to 1998 and later vehicles that have the FSS (Flexible Service System). MB diesels of this vintage run on direct injection technology and, thus, do not have pre-chambers. As such, the levels of soot accumulation over time are GREATLY reduced. For this reason, running longer drain intervals with synthetic oil makes sense.

For indirect injection diesels, which includes all MB diesels prior to '95 (with the exception of the '95 S350-OM603.97), synthetic oils will assist with cold weather starting and WILL reduce engine wear over time. However, soot accumulation and oil contamination will still occur. It makes sense in this case to change the oil more frequently. I use Mobil 1 and change every 3-4000k mi.

All this, of course, is IMHO. Happy motoring...

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Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

For oil consuming diesels some people (including big diesels) use a para-synthetic oil; part dino, part synthetic. This gives some advantages of synthetic at a lower price that 100% synthetic so the oil usage doesen't use up all their money.

The following are links to the major manufacturers of synthetic motor oils.

First, there's AMSOIL's Marketing Manager's personal webpage.:

http://www.cp.duluth.mn.us/~ennyman/a-pages.html

Then Mobil DelVac 1.:

http://www.mobil.com/mobil_lubes/onhighway/products_services/delvac1/index.html

Then RedLine.:

http://www.redlineoil.com/whyredline.htm

Finally, Lubro-Moly's parent company website. Note that they make a synthetic diesel oil, as well as a regular diesel engine oil and even a 0W40 multi viscosity oil.:

http://www.liqui-moly.de./ani.htm

As far as commercial trucks and what they use, there is no factual comparison to be made of Mercedes diesel engines to Detroit, Caterpillar, and or Cummins commercial diesel engines. But for the sake of information exchange, most heavy trucks use Larry Bible's favorite oil, Chevron DELO 400. Many owner-operators have changed to DelVac 1 for the fuel economy, extended drain interval, ease of starting in low-temperature climates, and reduced engine wear. The only reason to not use DelVac 1 in your Mercedes is that it can be hard to find an outlet for you to buy it from. Heavy trucks change conventional motor oil every 15 to 30 thousand miles depending upon how they are used. Cross-country driving allows for the longest change interval, as the truck is being used more, and operated at a steadier constant road speed. Mobil claims that for long-haul trucks, DelVac 1 allows for an increase to 60,000 miles. Again, a comparison of diesel trucks to our Mercedes vehicles is ludicrous.

Another benefit to consider in using synthetic oil is that it contains no wax, or paraffin to combine with combustion by-pruducts and form sludge. Also, it helps to combat the formation of acid that results from the naturally occuring condensation of water vapor produced during the combustion process. Add to that the better detergent properties of the synthetic, along with the increased lubricity, and your engine will last longer, run better, stay cleaner inside, and will have less wear in the long run. But I would only change the oil filter when you change the oil, and not before.

I also recommend you buy the best diesel fuel with the highest cetane rating that is available to you in your area, add a proper fuel additive like Redline Diesel Fuel Catalyst, or 85+ (same thing, different label), you will increase your fuel's cetane rating, and it will burn more efficiently, thereby reducing the amount of soot produced by combustion, and accumulated in your crankcase. Mercedes Benz diesel engines require much higher cetane fuel than is generally available in this country.

My '82 300SD has had Redline or Mobil 1 synthetic motor oil in it for the last 80,000 miles. It also has Redline in the transmission and the differential. The owners manual recommends a 5,000 mile drain interval when using conventional motor oil like Castrol. Redline has told me that I can safely extend that to 15 to 18 thousand miles when using their synthetic. I have decided to stay with the 5,000 to 7,500 mile drain interval for the time being.

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Scott Longston
Northern California Wine Country...
"Turbos whistle, grapes wine..."

Goldenbear--Is the 1995 S-350 direct injection?

oldsouth,

I stand corrected. Thank you for pointing out my error. I meant to state that all '95 and earlier MB diesels are indirect injection, with the exception of the '95 E300 D (OM606.10 engine).

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Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

The long haulers using synthetic oils and running such long miles between changes do not attribute this to the motor oil.
The long life of thier oils comes from Superior filtration and continious engine on time.
Take note when at a rest stop where these trucks are parked, the engine running satisfies many requirements one being not to allow the engine to cool and condensation to form.
The large filters can be seen also. These filters have a varied type of filter media everything from clothe/paper to fullers earth. Some filters also are heated by the exhaust gases.
Trucker's oil filtering can be so complete that dino oil can be reduced to base mineral.
In our passenger car diesel engines if the filtration were adequate we too could run these long miles or forever, gas engines as well.
Since I don't have a compression ignition but a spark ignition engine I'll mind my own business.
And Scott, stick to making or at least drinking the Napa Juice.
Nice hearing from you too Johson.
Happy Trails Beep Beep from Houston
Don, El Cheapo

Guys if you really want to treat your diesel special then add a bypass filter to your MB and run synthetic Delvac 1 or Amsoil series 3000. One of the reasons the big rigs don't change their oil as often as we do in our own cars is that tend to only change their primary and bypass filters then top off with additional oil to compensate for oil lost during filter change. Some of these rigs may go up to 100k before they change all their oil and filters. I am not suggesting any of you try the 100k scenario, but if you are really serious about the longevity of your diesel then I would seriously look at adding the bypass filtering system to your car in conjunction with the primary filter. Johnny

Please show me some specific data, and/or some proof of what you contend. I owned a company that had both tractor-trailer rigs and buses out on the road in the U.S. and Canada. And I've driven them too. I know from experience what I am saying is correct.

Fullers Earth? DON! Fullers Earth is so abrasive that it is used as a drilling media for starting oil wells! There is no way that stuff is in diesel truck oil filters! If you really hate someone, put Fuller's Earth in their crankcase, or fuel system and see how long their engine will last. The filters used in commercial vehicles are just like the ones that are used on all other vehicles. And those trucks idling at rest stops are doing so to keep the heaters and A/C running. No other reason. In fact, I know of several fleets where excessive idling time is reason for dismissal of a driver...

As for oil filters being heated by exhaust gases, just where did you hear that? The oil filters come nowhere near exhaust gas, and part of their job is to cool the oil, not heat it! The only pre-heating done to the oil system is done via block heaters that heat the cooling system in the winter. In fact, the massive filters you see on the outside of some older trucks are the air filter, and the oil coolers. Some even still have an oil bath air filter. But, the engine oil filters are actually in the engine compartment.

And as for 100 THOUSAND mile oil changes, I have been working with commercial diesel engines for over 30 years. No one goes 100,000 miles without an oil change unless they want to do an engine change real soon too. Oil is changed just as I have previously stated in my last posting. In fact, those extended oil drain intervals ae ONLY possible due to advanced formulation of engine oils. In the old days, the trucks required an oil change about every 6,000 miles. The difference in drain interval today is strictly based on the properties of the oils. And when those filters are changed, the oil is also changed just like any other vehicle. Filtration is of no use to oil that has literally broken down, and worn out it's ability to lubricate. Once the oil has lost it's ability to provide heat dissapation, lubricity and cushioning to your motor, there isn't an additive, filter or act of god that will do what a simple oil change will do.

Please stop comparing 350 & 450 HP truck engines to Mercedes Benz diesels! THERE IS NO LOGICAL COMPARISON!!!!

You might as well compare a Palomino to a Zebra...

[Edited by longston on 04-21-2001 at 04:39 AM]

__________________

Scott Longston
Northern California Wine Country...
"Turbos whistle, grapes wine..."