Mobil 1 75W-90 - PeachParts Mercedes-Benz Forum

tobybul · #1 02-02-2007, 08:32 PM

Changed the differential oil today to Mobil 1 75W-90 on the 85D. Seemed to have a noticable, smoother effect.

BTW, the differential drain and fill nuts take a 14mm allen.

Also, blew compressed air in to the fill hole to drain out the old oil as much as possible. I ended up getting a 1/2" drive hex bit set from AZ that had 12, 14 & 17mm bits for $9.99. This is the way to go.

Jeremy5848 · #2 02-02-2007, 08:59 PM

Quote:

Originally Posted by tobybul

... I ended up getting a 1/2" drive hex bit set from AZ that had 12, 14 & 17mm bits for $9.99. This is the way to go.

Do you have a part number for the Allen set? I can't find it in their web site, must be searching the wrong keywords.

I've noticed no difference in my 123 car with Mobil-1 75W-90 in the diff. No noise before, none now. (I suppose that's good.

) A month and a half and 2000 miles on the new oil.

Matt L · #3 02-02-2007, 09:01 PM

I got a set of SK 1/2" drive keys. They were somewhat more expensive...

I have yet to use them. I'm waiting for a decent day to help the fluid get hot during a drive.

mobetta · #4 02-02-2007, 10:31 PM

I posted the autozone PN here somewhere, last spring.... on a thread that i didnt start....

tarbe · #5 02-02-2007, 11:12 PM

Do you have dry air? I hope there wasn't any water getting sprayed into your diff.

DeliveryValve · #6 02-03-2007, 12:15 AM

Autozone's "OEM" tools 1/2 inch hex bit. sizes 12, 14, and 17mm stock number is 76812-25417. I purchased these for $10.00 sometime ago and have been very good. I even used the 14mm with my impact wrench and they survived.

But my other question is, I had Mobil 1 in my differential. Earlier this week I started removing my axels to replace the boots (which BTW is another story). I drained the fluid in the differential and the fluid coming out looked fine. But when I opened the cover (which is the first time I did this on this car), I see foam inside there. Has anybody also found foam in their diff while using Mobil 1?

This brings me to my confusion/horor in this link I pick up from ForcedInduction in another thread where is showed foam in a Pennzoil product.

http://www.bobistheoilguy.com/images/lucas/lucas.htm

If nobody had the same results then my guess I didn't drain it out fully when I changed it out originally.

Jeremy5848 · #7 02-03-2007, 12:50 AM

Synthetic oils are "supposed" to mix completely with petroleum-based products. I've also heard that synthetics will remove crud that has deposited on surfaces after years of dino oil use; perhaps the foam is a byproduct of that process? It is certainly not something I would have expected and you are right to be concerned. Seems to me that over-filling an engine will cause foaming of the oil (thrashed up by the crankshaft, as I recall). Don't know if the differential would also be subject to such a problem and can't see how you could over fill the diff anyway, unless you stood the car on its nose so the fill plug was straight up.

tobybul · #8 02-03-2007, 09:05 AM

Quote:

Originally Posted by rmarzan

Autozone's "OEM" tools 1/2 inch hex bit. sizes 12, 14, and 17mm stock number is 76812-25417. I purchased these for $10.00 sometime ago and have been very good. I even used the 14mm with my impact wrench and they survived.....

Yep, thats the item number although the packaging on mine only says 25417. Its also lifetime warranty. It reads 1/2" DRIVE METRIC HEX BIT SET.

tobybul · #9 02-03-2007, 09:08 AM

Quote:

Originally Posted by tarbe

Do you have dry air? I hope there wasn't any water getting sprayed into your diff.

I thought about that when I was doing doing it. Although not the best test, I did a visual on it first also blew it out it for a few seconds b4 putting it in the diff.

Good comment.

jim16671836 · #10 02-03-2007, 09:29 AM

I thought the differentials in the 70's & 80's models all used a lighter weight oil. I have drained about 20 and don't remember any heavy weight oil.. Jim

lkchris · #11 02-03-2007, 11:07 AM

Quote:

Originally Posted by tobybul

BTW, the differential drain and fill nuts take a 14mm allen.

It's the German standard. 14mm on BMWs, too.

BTW, Mercedes has never approved synthetic oils for its differentials.

#12 02-03-2007, 04:13 PM

Quote:

Originally Posted by lkchris

BTW, Mercedes has never approved synthetic oils for its differentials.

Because they didn't exist when these cars were made.

tarbe · #13 02-03-2007, 10:02 PM

Quote:

Originally Posted by rmarzan

I see foam inside there. Has anybody also found foam in their diff while using Mobil 1?

That almost looks to me like there was some water in there with the oil.

300SDog · #14 02-03-2007, 11:59 PM

Quote:

Originally Posted by Jeremy5848

I've also heard that synthetics will remove crud that has deposited on surfaces after years of dino oil use;

True for the crankcase, probly true for the pumpkin too. Am wondering about this myself changing to synth in the diff just over a year ago in the 240D - maybe I'll do another oil change with synthetic (to get rid of loosened crud) and then leave it alone for the next 50k miles.

Ken300D · #15 02-04-2007, 08:10 AM

Yes, synthetic gear oil visibly removes accumulations of sludge from differentials. You'll see the difference should you need to remove the cover.

In switching over to the synthetic gear oil, which I highly recommend, I also recommend running it for about a year or so and then changing it again. Change when hot in the summer after a good drive - this suspends the particles in the oil - better for them to drain out with the oil.

Ken300D