Motor Oil Question - PeachParts Mercedes-Benz Forum

tobybul · #1 12-20-2010, 08:11 PM

Just wondering what non-diesel motor oil would do if used on the 300D's. By non-diesel I mean motor oil used on gas engines (5w30, 10w30, etc).

79Mercy · #2 12-20-2010, 08:15 PM

No reason not to use a diesel rated oil, you can get 5W40 and 15W40 diesel oils. However the dealers used to use 10W-40 and 20W-50 Castrol GTX years ago. However back then the gasser oils had a lot of zinc in them.

Jeremy5848 · #3 12-20-2010, 08:15 PM

It would probably be OK until it loaded up with soot. You might get a thousand miles or two -- perhaps someone has experience to share?

Oldwolf · #4 12-20-2010, 08:22 PM

Rotella T 10W30 is diesel rated and in the weight class you mentioned.

Also, many SM rated oils are also CF rated so I would at least pick one that has that rating.

If I had to do it I'd pick something like Mobil Clean 5000 10W40 which is a CF rated oil I think.

http://www.mobiloil.com/USA-English/MotorOil/Oils/Mobil_Clean_5000_10W-40.aspx

Cr from Texas · #5 12-20-2010, 08:35 PM

Quote:

Originally Posted by 79Mercy

No reason not to use a diesel rated oil, you can get 5W40 and 15W40 diesel oils. However the dealers used to use 10W-40 and 20W-50 Castrol GTX years ago. However back then the gasser oils had a lot of zinc in them.

I'll admit I got caught on this one. In 1983, the dealer recommended 20W-50 Castrol GTX and I used it religiously until I found this forum. In 1983, Castrol GTX carried a CD (diesel) rating. I don't know when it happened but the CD rating got dropped. Not knowing better, I kept using the oil. I've observed no ill effects but I also always changed oil and filter every 3k miles. I'm now using Rotella 15W40. No change noted.

pawoSD · #6 12-20-2010, 10:23 PM

Quote:

Originally Posted by tobybul

Just wondering what non-diesel motor oil would do if used on the 300D's. By non-diesel I mean motor oil used on gas engines (5w30, 10w30, etc).

Why? Rotella 5w40 synthetic diesel oil can be bought for $18.99 a gallon at meijer and is good for 5-6k changes in a 617.......

Brian77 · #7 12-21-2010, 12:08 AM

I tried Rotella 5w-40 on my '85 300SD but think that it was too thin for my old valve stem seals and other motor seals. I found that it seeped more oil from the motor to the outside and also through the exhaust. I use nonsynthetic 15w-40 Rotella during the summer. The car sits outside and was looking for a compromise to allow it to start easier during the winter here in Delaware. I switched to 10w-40 for the winter because I cannot seem to find a brand of oil sold around here that is lighter, not synthetic and has a CF rating. I see the post about Rotella 10w-30 and will have to check this out. I change my oil every 3K. I have not noticed any difference. I am sure a lot of people will disagree with my choice.

babyjames · #8 12-21-2010, 12:17 AM

Why not synthetic in the winter, dino in the summer? If easier starting is what you're after, synthetic oils are the obvious choice.

I've got Lubro Moly 5W40 Synthoil Premium in all my (running) cars. They seem to like it, and I've noticed, if anything, a reduction in consumption....

Jay.

europower · #9 12-21-2010, 01:52 AM

I have tried lubromoly, delo, rotella mobil 1 etc and nothing compares to sewpco 14w40 supreme formula.This oil you can feel.
Its a bit hard to find but worth every penny, Ups uses it on their trucks.
heres a link to their website.
http://www.swepcousa.com/lubesite/products/306.htm

Oldwolf · #10 12-21-2010, 06:36 AM

Many may not agree with my next statement, but I have done it many times with no issues.

Blend your own semi syn oil. Mix 15w40 with 5w40 (or 0w40) to get the weight you want. Might as well stick with the same brand name when doing this but even that is not necessary. Let me know if interested, there is a neat blending calculator online I can point you to.

C Sean Watts · #11 12-21-2010, 08:12 AM

Many oils that may be labeled on the front..."for sports cars/SUV/high mileage/etc" Are rated for BOTH gasoline and diesel engines. You'll have to check the back, specifically the API (American Petroleum Institute) label.
It's the little 'circle in a circle' with letters in it. The letters tell you...
You'll see something like "SF, SG/CD, CF" The "S" indicates for use in spark ignition engines (gasoline.) The "C" indicates for use in compression engines (Diesel.) NOT ALL OILS ARE DUAL RATED, so read carefully. The letters following the "S" or "C" correspond to lists of other chemical related specifications, API makes that public so I'm sure it's on the forum somewhere...

tobybul · #12 12-21-2010, 09:08 AM

thats good info sean. always wondered wht the S and C meant. this means that many oils I thought were just for gas (S) are apparenty for diesel (C) also.

Reason i brought up the question is when i changed oil over the weeked, I noticed the old oil seemed a bit pasty (i did warm up the engine a bit b4 changing). So I decided to mix about 30% 10w40 synthetic (CF) with the 15w40 with the new oil. I noticed it seems smoother and also started right away this morning after leaving it out all night. I know that with the 15w40 I would have had to plug it in.

I be watching for the multi-rated oil next time.

Oldwolf · #13 12-21-2010, 09:23 AM

You are already blending with good results.

bobodaclown · #14 12-21-2010, 11:31 AM

CF Indirect-Injected Diesel Engine Service Service typical of indirect-injection diesel engines and other diesel engines that use a broad range of fuel types, including those using fuel with high sulfur content; for example, over 0.5% wt. Effective control of piston deposits, wear and copper-containing bearing corrosion is essential for these engines, which may be naturally aspirated, turbocharged or supercharged. Oils designated for this service have been in existence since 1994 and may be used when API Service Category CD is recommended.

http://www.upmpg.com/motor_oil_rate_gas.htm

JHZR2 · #15 12-21-2010, 04:07 PM

Not all oils are rated for spark ("S") and compression ("C") service. What you loose these days is the levels of dispersants used to stabilize soot and prevent it from agglomerating into larger particles which could cause wear. Note that color does not indicate oil health or condition. Also, zinc/phosphorous additives (ZDDP) are severely reduced in spark only formulations (and low saps diesel formulations) to protect emissions equipment. Now, ZDDP is obsolete and cheap technology, and only in flat tapper cam situations is it really needed for protection. Alternates that are better exist, so it's not something I sweat excessively, but since our applications don't have emissions equipment, it doesn't hurt to have it in the mix.

My main concern is ability to deal with soot, which is very important on the 617 and less so as the engines get to newer models.