Normally I wouldn't even ask, but all the 15w-40 oils say "truck" oil on it. I think even the mobile 1 says "truck". It may not be officially approved, but how different can mobile's synthetic formulas be?

For MY2005 and newer use MB Spec 229.5 oils and for MY2004 and older use MB Spec 229.3 or 229.5. Mobil 1 Synthetic 0W-40 ECF (European Car Formula) meets both these specs. You can use different viscosities of an approved oil but in the Continental US + Hawaii the 0W-40 is appropriate. These approved oils are designed to be the best for easy starting, minimal engine wear and best gas mileage.

You can put whatever you want in and your engine isn't going to blow up 30 mi down the road. As long as you use a quality oil any downside will be harder starting, more engine wear and lower gas mileage which may or may not be important to you. If you plan/want to keep your car for a long time, I'd suggest using the approved oil.

Perhaps I am confused. But Chevy trucks have used the LS1 engine that was also used in cars. So,, truck oil vs car oil?

There is a Mobile 1 full synthetic truck oil that meets the MB car spec. So if it meets the spec you can use it. I would not just use any off the shelf oil but if you have to do so go to the shorter oil change frequency as dictated if your FSS is so equipped.

There are many people who own mercedes and due to location can not buy approved oils so always use the best you can if you can't meet the spec due to availability with the shorter oil change frequency.

Sorry, I wasn't very clear. I don't want to run 0w-40 in the summer. I want a thicker base stock (yes I know it's synthetic). I have seen 10w-40 mobile 1, but since MB recommends 15w-50 mobile 1 (which was the first oil approved for MB's extended oil changes I believe), I was thinking 15w-40 would be the best of both worlds; a thick base but better MPG then 50w.

While in walmart, the mobile 1 15w-40 had "for trucks" on it, I'm hoping it's just for marketing. More or less I would think all mobile one is created equal, right?

No,, the 10w30 M1 full syn I use in my Corvette is not approved for extended oil frequency in my E500. I use 0w40 year round in the MB.

It's really not necessary. If you go to any of the major oil cos. websites (Mobil, Valvoline, etc.) and check out the FAQ's you'll see that using a heavier oil in the summer is a misunderstanding. I know it sounds right intuition wise, but look at it this way. The inside of your engine is much hotter than the air outside (by 100's of degrees) and the cooling system (if working well) controls the engine temperature to the same range summer OR winter.

The important number in oil viscosity spec is the first one. That is the 0 in 0W-40. Choose your oil based on that number and the coldest temperature you expect before the next oil change. 0W-40 is good to -13F so it is appropriate for ConUS + Hawaii for all MB vehicles.

As always it's your car and your money so you make the final decision.

You should be using an "approved" oil -- see: http://bevo.mercedes-benz.com/bevoli...ets-sort1.html
for the 229.3, 229.5 and 229.51 (whichever is applicable to your car).

BTW, when you're looking for "thicker" oils, you need to compare the spec sheets for the viscosity at 100 deg C. The 40 deg C values are usually given so you can calculate the viscosity index of the oil. According to the M1 site, 0W-40 is 14cSt, and 15w-50 is 18.1 cSt (at 100 deg C).

Oil chemistry is complicated and when there's a multi grade oil, the two specs have to be met, for example: the "0W" and the "40". To do this (in a simple sense) is to use a less viscous base stock that will allow the "0W" spec to be met and then add viscosity index improvers (and other stuff) to meet the "40" spec. The bad news is that the VIIs will shear under high stress conditions causing the oil not to meet its 100 deg C value -- the good news is that synthetic base stocks tend to have better, inherent viscosity indices (prior to formulation) so less VIIs are needed.

Hope this helps.

Regards,
paul...

Thank you for the technical responses. Go figure that I haven't been to walmart since I posted this thread. I'm starting to think that the 15w-40 oils said "diesel" on them not "truck". I will try and make it to an auto parts store tomorrow to check. What I was also worried is that the oil for diesel engines might have different additives than normal oil.

I probably won't take a chance with my MB, but I might try 15w-40 "for truck/diesel" in one of my other cars.

Before you buy a "truck/diesel" oil for your gas cars, check the oil rating to make sure it meets the API SL or SM rating in addition to the diesel CI-4 or CJ-4 rating. Some oils can be used in both types of engines as oil companies are aware that there are mixed fleets (diesel & gas trucks) that many companies have and would like to have one oil for both.

Regards,
paul...

There are ONLY TWO Mobil 1 oils suitable and approved for use in Mercedes engines (diesel or gas) and those are 0W-40 European Formula and 5W-40 Formula M ESP. (this in USA)

If Mercedes Specification 229.5 or 229.51 is not PRINTED ON THE BOTTLE, the oil is not suitable for Mercedes.

Use of "50 weight" oil is so 20th century and is frankly irrelevant to modern engines.

See http://www.startekinfo.com/StarTek/o...stedDocId=9511

Hmm, guess I should have read this post before I bought the oil..

Did an oil and filter change today in my 2004 E-500 and used
Mobil 1, 15W-50.
Checked the MB manual first, and the viscosity was indeed OK.

Looking at this thread and checking the bottle, I see no 229.5 or .51..

The car has 80.3K miles and will be driven in South Florida only.

Did I waste $50.00 on bad oil or what...?

You did.

20th century "father's Oldsmobile" knowledge is simply irrelevant.

Current studies, for example, also show that it's detrimental to change oil sooner versus later, too.

http://papers.sae.org/2007-01-4133/

Just do what Mercedes recommends--none of us here have more knowledge or better advice.

If his manual showed 15-40 as a recommended oil than he did good.

Not all cars are new.

How long has 0-40 been available?

Don't worry, your engine won't blow up. Drive the snot out of it. Ps - use Gold Cap M1.

Absolutely:

I went by the book, page 5 of Factory "Approved Service Products" where the "Viscosity Grades for Motor Oils" chart is displayed.
15W-50 is listed for a range of temperatures from -15 C to +30 C and above.

I did miss the small print on 3 where FSS or FFS Plus is being discussed and Mobile 1 0W-40 at 229.5 and 229.3 is the only MB approved oils.

Oh well, blew $50.00 on oil. Could have been worse I guess.

Yeah, it won't blow up, but if the tolerances are small and the oil pressure gets too high, it could blow a seal...No?

Or is the 0W-40 to meet gas milage standards more than engine health?

Thanks for the advise gents, this forum has been great.