Does anyone have an opinion on using synthetic oil in a 300SD? I hear that some diesel owners love synthetic oil, but I would think that all the soot produced by a diesel would make frequent oil changes more important? Jacob Wissler Jr www.jacobwissler.com

no problems. mobil 1 15/50 will do wonders.

On my 82 300SD (just turned 200,000), I ran Mobil 1 (0-30w) last winter during the coldest months of Minnesota. Stuff ran out of that engine like a sieve, puddles of oil everywhere. I think it depends on if you have any leaks or not. For the money, personally I wouldnt bother, except as a nice, clean out your engines innards flush kind of thing. Im happy running that Quaker state HDX diesel fleet oil, you can get it in 4 gallon containers at Wal mart for around $8 and nice german filter (in stp box) at autozone for around $9.
I change mine around every 3000 miles. Save your money, go to restaurants or get some nice new clothes..

...still costs under $20. Synthetic oils cost $4-12 per quart. You can leave them in for longer intervals, perform oil analysis, etc. and be pretty well-lubricated and pretty safe Some people just love this kind of thing. Bypass filter systems flat work. For some users this is really convenient.

But when Pennzoil LongLife or Delo 400 is available for so little you can change the oil & filter 3 times in 15K miles for about what one synthetic change and one oil analysis costs. There is no question that 24 quarts of oil and three filters will probably handle any lubrication-related problems that may arise in the normal course of operation.

And that is a good thing! IMOH

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'91 420 SEL @ 199K, '92 SVX @ 181K, '93 SC400 @ 86K, '93 Kaw ZX-11 @ 30K, '87 F250 @ 181K , 2001 Valkyrie Interstate @ 6K, Y2K Honda NightHawk 250 with 1.5K, '88 420SEL I.@ 179K & the 2nd latest, an '88 420SEL II.@ 210K runnin' parts car, '85 F150 300/NP435

Diesel engines require a richer additive package in the motor oil than spark ignition engines. The American Petroleum Institute works with manufacturers to develop oil standards and the current service classification for diesel engines is CI-4.

Most popular synthetics are designed for spark ignition engines and the current API standard is SL. Though CI-4 oils may be available with synthetic base stocks, I'm not aware of any off the top of my head. Most of the national and house brands are mineral oil based.

For all the "experts" who have participated in the seemingly limitless discussions on oil, few realize that the most important feature of a motor oil is the additive package, NOT the base stock.

Prior responses gave you some recommendations on CI-4 oils. I'm not terribly picky about brands, but you should use a CI-4 oil in any diesel, and you should follow the OEM's recommended change interval. Look at the label to find the API logo and service classification.

If you want to learn more about motor and gear oil specifications go to www.api.org

Duke

this is why mercedes states that mobil 1 15/50 and now 0/40
is recommended. not any of their other weights.

...are found in both current Pennzoil LongLife & Delo 400
15W-40 weights. Along with a host of other diesel specs.

I would doubt that the previous formulations at SJ/CH-4 would prove any less excellent in any 300SD. Let us not forget that the newest oil recommendations from MB are primarilly established for their newest models as they are introduced.

There is a lot of difference in the lubricating needs between an 80's 420SEL & a 2003 CLK55, but not very much between the 420SEL and a 300SD.

IMHO, of course.

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'91 420 SEL @ 199K, '92 SVX @ 181K, '93 SC400 @ 86K, '93 Kaw ZX-11 @ 30K, '87 F250 @ 181K , 2001 Valkyrie Interstate @ 6K, Y2K Honda NightHawk 250 with 1.5K, '88 420SEL I.@ 179K & the 2nd latest, an '88 420SEL II.@ 210K runnin' parts car, '85 F150 300/NP435

Mobil Delvac 1 Synthetic is formulated for Diesels but it's very hard to find. The best I could do was at a lubricant wholesaler who'd sell me a crate 6(?) gallons for $85.

Sixto
91 300SE
87 300SDL
83 300SD

Shell and Chevron also produce synthetic motor oils which have the additive package appropriate for a diesel, and which carry an appropriate C rating such as CI-4.

(Contrast to the S ratings found on non-diesel-rated oils, like "SL" motor oils -- the C prefix is for Compression ignition, S for Spark ignition. Most diesel oils also carry an S rating and are fine in a gasoline engine; the converse does not hold.)

The original thought is also correct: diesels do need an additive package to deal with all of the soot they infiltrate the oil with. Mostly extra detergents and dispersants, as I recall. Not all synthetics have these, just as only some nonsynthetics do.

s/b

For those of you looking for Delvac 1 try the national truckstops. Flying J and TCA both carry it. I am sure others do. And the can be found around just about every major city.

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Art Bourget

1983 300SD
1st In Class - Starfest Concours 2004
1st In Class - StarTrack Concours 2003
1983 300TDT
1985 300D

MBCA - Niagara Section

Check this out http://www.canadiandriver.com/articles/pb/synthetic.htm

I use Amsoil synthetic in all my MB's, engines, gear boxs and P/S pumps and am very pleased.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

You didn't mention how many miles your car has. Obviously this thread is already turning into another oil debate, so I will not add any fuel to the fire about syn. vs. dino oil. With that said, regardless of brand, oil designed for diesels is ALWAYS 15W-40. I am in the Air Force, working on jets. The trucks we drive on the ramp are 2001 Chevy V8 diesels, they call for 15W-40. I don't know the significance of this particular weight, because if "diesel rated" oil is due to the special additives, then why can't that be added to say 5W-30 or 10W-30 etc.? Since I am not an oil engineer, I don't know why 15W-40 is the universal weight oil for diesels. What I do know is that any brand 15W-40 oil is also rated for gas engines, but not every other weight oil is rated for diesels. There is something about this particular weight that makes it a truely universal oil for all engines.

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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)
MBCA member

The API motor oil rating is based on the additive package required to pass the test suite for diesel or gasoline engines, not the SAE viscosity. SAE 15W-40 can be considered a "year round" oil for most parts of the country. The reason it is probably not 10W-40 is because a greater concentration of viscosity index improvers would be required, which are consumed with use and tend to leave deposits. Some OEMs no longer recommend 10W-40 for this reason.

CI-4 oils are also commonly available in straight SAE 30 and 40 grades. Synthetic base CI-4 oils probably have a wider viscosity range as is the case for SL motor oils because the synthetic base stocks have a wider viscosity range without the addition of, or with very small amounts of VI improvers.

Motor oil packaging contains the API symbol, which states the specification(s) that the oil meets.

Duke