Gawd, I hate to risk starting an oil thread, but here goes.

I don't have any recent MB data sheets. What is the current recommendation for oil viscosity for the M104 engine? The older data sheets I have seen recommend 10w-40, 15w-40, 20w-50 for different climates. But when I have the dealer service my M112 engined car (hey, it's included in the cost of the car...) they use exclusively Mobil 1 0w-40. So does this latest recommended oil also apply to the m104? BTW, I noticed while browsing at the McParts store that M1 0w-40 does not carry the energy conserving starburst symbol - interesting.

Please note that I'm not asking your opinion on which oil or which brand of oil to use, I want to know which viscosities MB currently recommends for the m104. I'm in the DFW metrmess, so need to deal with a temperature range of perhaps 15F during the winter to 105F during the summer.

Thx,

- JimY

Hi Jim. You might want to click on:

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

Heres what ALLData has to say about the 3.2L m104 (probably all mercedes engines as a matter of fact)

http://www.190revolution.net/prem/skiier3_9/Pictures/Oil%20Recommendations.pdf

Jim,

The MB dealers have 0W40 Mobil One in their fancy shopwide oil dispensing system. That is why they recommend it. This covers a pretty good temp range and is probably okay.

That said, oil weight is pretty fundamental in these engines. Many very new engines with roller lifters and some other considerations require lighter oils, but for the 104 I would go by the generic chart, a copy of which is linked in the post previous to this one. It indicates 15W40 which would be a dino oil and 15W50 which would be a synthetic.

In our climate for your engine I just don't think you could go wrong with those weights. Once Winter gets here it wouldn't hurt to lighten up a notch to maybe 10W30 or whatever is the next lighter weight in the alldata chart.

I wouldn't get too wrapped around the axle over this. Pick your favorite brand premium oil in a reasonable weight for the season, keep it changed and it will probably run forever given the way you maintain your cars.

Have a great day,

Thanks for the input all. There's a pretty good related discussion going on over here: Mercedes-Benz oil specification

I ask because I changed the oil in the m104 last week using M1 0w-40. That's what MB recommends for M112/M113 and newer engines, so I chose it. (I exclusively use M1 products - different discussion, different reasons.) This week it occurred to me to question whether it was actually an appropriate choice. Looks like the answer is yeah, it's fine. M1 15w-50 would be fine year 'round in Dallas, as would M1 5w-40 (which is really repackaged Delvac 1 - best choice for a diesel, but sadly I am diesel-less these days.)

- JimY

Below is something I've posted before on this issue. Only change is I now use the 15W-50 in my ML too most of the year.

This topic comes up every now and again on the Rennlist 993 Forum. He's a review by a knowledgeable person regarding this issue and the differences between OW-40 vs. 15W-50. Personally I use OW-40 in my ML and 15W-50 in my Porsche and my 300E.

"0W-40 is probably the perfect all around choice for 98% of street driven 993s. I think it does have an Achilles heel that make it not so good for some owners, of whom there is an especially high incidence on the Rennlist forums.

To get a 0W-40, even starting with a synthetic base stock, you must begin with a rather thin oil, probably what would be the equivalent of a 0W-20. Then you add viscosity extenders to it, which are long chain organic molecules that unfold as they meet higher temperatures. This keeps the oil from thinning as fast as it would normally as it heats up, and allows it to have the 40 weight rating at 100 degrees Celsius.

One problem with viscosity extenders is that they aren't lubricants themselves, so their volume displaces the lubricating base stock, and the lubricity of the resulting oil is actually a little less. The bigger problem is that under high temperature, high shear conditions (high rpm!) these molecules are sheared apart and destroyed - over time. As these molecules are destroyed, the oil becomes thinner at high temperatures, so what was originally a 0W-40 oil starts approaching the viscosity of the original base stock - the 0W-20 stuff. This is not good for continued use at high temperatures and loads.

This is probably unlikely to happen to 0W-40 to a significant extent under normal street use within a recommended oil change interval. But if you drive your car hard on the streets of Phoenix in the summer, or regularly take your 993 to the track for DE events, 0W-40 might not hold up very well. This is why track guys like synthetic 15W-50, which has a higher viscosity base stock, and uses little (maybe none) added viscosity extender and will provide proper protection to the engine under "race" type conditions for a longer time than 0W-40.

So you see why Mobile 1 0W-40 might be the perfect oil for GJ, but not at all the right one for Greg's race car. There are no simple answers!"