synthetic oil grade for diesels/winter
 

Where I live, it often drops to -20 or colder in winter. What grade synthetic oil should I use in my 1984 MB300SD?

Your best bet is to go to Mobil1.com and see which weight would cover that temp. range. Normally 15W-40 is the universal conventional oil weight. Your owner's manual will list various weights based on temps., the problem is those are based on conventional oil. I checked the owner's manual for my '83 TD (same engine) and the chart only goes down to -4 f. and for that it list 5W-30. Again, this is based on dino oil. I also own a 1987 TD and I recently switched to Mobil 1 15W-50, but I am down here in NJ, where it generally only gets down to 20 degs. in the winter.
BTW I mention Mobil 1 because it is more readily available. You may be able to use 0W-40 which you can sometimes find at a Walmart.

Delvac 1:D

Castrol Syntec 5W50 or Shell synthetic Rotella 5W40 works for me in the winter.

The Rotella is often on special at Walmart for about $12 a gallon. That's probably your best buy.

P E H

I agree with P.E.

I use Rotella 5w40 in all my diesels in the winter months and pay the $12 per gallon when on sale. Just bought about 10 gallons.

The engines spin much easier upon start up.

Don

Dear paulgill:

Do not use the regular (BLUE cap) Mobil 1 synthetic oil (any grade)
in your 300SD diesel car. If you really want Mobil 1, you need to get the RED cap Mobil 1 oil bottles, because it contains the necessary soot control and detergent additives for diesel engines.

Castrol Syntec (any grade) is not perfect for your car either, even though it may have CF spec. The newest diesel oil spec is CI4.

I think the best synthetic oil for diesel cars is Delvac 1 and then Shell Rotella synthetic oil. They both have CI4 spec and are designed specifically for diesel engines.

Best regards,

Eric

Eric,

The cap color on Mobil 1 only denotes the weight (viscosity) of the oil. The extra soot control is only in Delvac 1 as that is especially made for Diesel engines. The red cap is 15W50. Green cap might be 10W40, not sure though

Castrol Syntec 5W50 has done well for me in my '79 300SD. It decreased the oil consumption from 3 quarts in 10,000 to 1 quart in 10,000 miles. This was over a period of 30,000 miles. I have no idea what oil was used before I got the car at 160,000 miles.

P E H

oh joy, here we go again!

First, the only Mobil synthetics approved for use in MB diesel engines are the 0W-40 (black cap), 15W-50 (red cap), and Delvac-1 5W-40. DO NOT use any of the xW-30 weights (silver, green, or blue caps). For winter use, even the 15W-50 will be fine in sub-zero temps. Stick a quart in your freezer and see for yourself how it pours. You'll gain almost *nothing* by using the super-thin stuff like 0W-40.

Second, Castrol Syntec and Shell Rotella "Synthetic" are not true synthetics. They are modified dino oils (Group III) that exhibit some of the properties of real synthetics (Group IV/V). They are cheaper to buy for a reason - they are inferior, and will break down sooner. If you change every 3-5k, they're probably fine. I would NOT attempt extended drains with these oils. I also seriously dislike their deceptive marketing tactics and refuse to buy them.

Third, any Cx-rated oil (CG, CH, CI, etc) is technically ok to use if it's xW-40 or xW-50, AFAICT. Never ever use non Cx-rated oil that only has an Sx-rating (SJ, SL, etc). Those Sx oils can't suspend the soot produced by a diesel.

IMO, Delvac-1 is probably about the "best" diesel oil out there. It can suspend nearly 4% soot, or about double what Mobil-1 can. The only other oils I know of that can suspend that much are Delvac-1300 and Delo-400, both dino oils. Amsoil and RedLine also make top-quality synthetics, but they're a little more costly, and I honestly don't know what their soot suspension limit is (but I assume it's at least 2%).

drain intervales?
 

Thanks for the info...now, how long can I go between oil changes using Delvac 1?

long time if you wish.....

Best way is to perform an oil analysis everytime you change your oil. I went about 5K on my first run, sampled the oil and it came back like new. Will try to sample again at 7500K interval.

The only way to determine max drain interval is with oil analysis. Every engine produces different amounts of soot and other contamanints (sp?). On my 1987 engines, analysis shows I could probably change every 15-20kmi safely with Delvac-1. On my 1984, more like 10-15kmi because it produces more soot. This assumes that soot is the limit (which it usually is), and that TBN is ok, and other wear metals are normal. I usually change at 10kmi because that's 12-24 months of driving for me, and it's an easy number to remember (change at 230k, 240k, 250k, etc).

FWIW, Doc Booth (MBCA diesel tech advisor) mentioned that the OM60x engines with hydraulic lifters should have the oil changed when the soot reaches 2%, even if the oil used can suspend more (i.e., Delvac). I'm not sure where that recommendation came from (MB or elsewhere) or what the exact reason is. Supposedly this doesn't apply to the older OM61x engines, those can go right up to whatever the oil's limit is.

I scanned some of my analysis reports, and posted them in PDF format here (scroll down to "oil...") :
http://www.meimann.com/docs/mercedes/


HTH,

Dave, I have to disagree with you on this point. I've never found Delvac 1 for less than $20 a gallon, and have paid as much as $25. Two cases of gallons, shipped to me from AvLube comes to $198. By contrast, I just bought 2 cases of Amsoil heavy duty marine and diesel engine oil (15W-40) for $165, including shipping and $20 for the preferred customer program. Subsequent purchases during the year will be even cheaper.

You should only use approved MB oils. M1 or D1 is probabaly your best bet.

http://www.whnet.com/4x4/oil.html

Rick,

Sorry, I'll elaborate. RedLine, AFAIK, is in the $6-$9 per quart range, and I've never found it cheaper. It seems to be EXCELLENT oil (probably better than Mobil or Amsoil) but I probably would never spend the extra money unless I had a 500E or Porsche (oh wait, those are the same.) :D I do use Red Line gear oils and their MTL, because Amsoil & Mobil is about the same cost.

Delvac is expensive to buy online. I can't find it cheap anywhere. I paid ~$22/gallon at the Mobil distributor in Sacramento, $88/case, plus tax (carry out, no shipping). Try your local CAT (Caterpillar) dealer also, they sell Delvac-1 with a CAT label.

Amsoil 15W-40 diesel oil is $60/case (four gallons) at the dealer/wholesale price. (MSRP is $80.40/case). They want $11 shipping for one case, or $18 for two cases. Plus your local sales tax. So yes, that is cheaper than Delvac-1. Especially if you do a Google search and find an Amsoil dealer that will give you the 6-month "trial" Preferred Customer status for *free*, which gives you the dealer price, and saves you the normal $10 fee! Try that next time instead of forking over the $20. :cool:

I'm stocked up for the next year or two. When I need to buy oil again, if I can't get Mobil-1 for $4.00-$4.50 per quart, I'll be buying Amsoil as well. Mobil recently jacked up the prices on both M-1 and D-1, which is making Amsoil look even better (unlessl Amsoil raises theirs too - d'oh!)

:) :) :)

I stir the pot a bit more.... Chevron Delo400 SYNTHETIC 5W-40. Not sure what "group" its in but its about $14 a gallon from my local distributor. I consider this a deal. No waiting Wally World to do a price rollback. There are two oils that are the kings of heavy duty diesel truck use. Rotella and Delo. Synthetic Delo should be that much better. I got it in all my vehicles without the Delvac "empty wallet" syndrome. RT