Replacing Oil in the Rear Axle (Differential)
 

I have a 1991 420 SEL and want to replace the original factory differential oil.. I know what is specified for the car (Owner's Manual) but I have some fresh 85W140 Heavy Duty Hypoid gear oil (generic brand, not Mercedes). SHould I use it or get the stuff from the dealership???

Thanks in advance for any replies or suggestions....

Bob Irving
Charlotte, NC

In maintaining over 1 million miles of MB products including one that I have taken over a half million miles, I have used nothing but Conoco Hypoid gear lube and I have never had any differential related problems.

My $0.02,

I suspect your owner's manual will tell you to use 85W-90 lube. If you use a synthetic such as Mobil 1 or Redline, use their 75W-90. Use any name brand lubricant so long as it's the correct viscosity.

This stuff is so cheap, it doesn't pay to use a no-name product of the wrong viscosity.

Red Line Lubricants
 

Where can I find Red Line Lubricants?

Thanks...

Bob Irving
Charlotte, NC
1991 Mercedes 420 SEL

Re: Red Line Lubricants
 

Bob, you can call Redline at 800-624-7958 or e-mail them at redline@redlineoil.com.

They also list the mail order companies on their site.

The PEP Boys here in NY carries Redline products, just not their engine oil. They do carry Water Wetter, the fuel njector cleaner and heavy weight gear oil. SO try there first. Chances are there's one near you.

P.S., the one near me will special order whatever they don't stock so ask about that if you don't see it.

Ron Brooks

I've used 85W-140 in the rear diff. of my 126 car for the past 60K.
No problems, but then I live in a very warm place - winter is non-existent. This weight of lube may be a bit too thick for cooler climates.

Bob: I note you're in Charlotte. My excellent independent -- Earle Whitton at Charlotte Star Service, 4225 Monroe Rd (just south of Wendover); tel 704-332-4111 -- just did a change of the differential oil in my daughter's 190E [I also have an '88 420SEL] last week and at my request put in synthetic oil.

If you choose to use Earle, he can get the synthetic for you (be sure to tell him that's what you want); for the 190E 3 units of the oil was $27.45 and the labor was $32.50 -- prices for a 420SEL might be slightly different.

Hope this is helpful.

Oh boy....here we go. Lubricants, like cameras, stereos, shoes, and everything else, tend to bring out the passion in people. You cannot 'win' an argument over lubricant selection. My choices have evolved using personal experience as well as selected recommendations of people I think are smarter than me.

As far as Red Line, you will pay a major premium for the privelege. Sure, if you have super-duty high stress special application, Red Line probably makes sense. But it amazes me how people will drive a car for 15 years and 150,000 miles and want to change to the best lube they can afford. It just doesn't pay out. All of the lubes that conform to the manufacturer specs will work just fine. Fact is, I've never heard of a diff that failed due to lubrication brand - from any of my friends or even discussed on many car forums. Also, Red Line is not that easy to find for many people. Why bother?

IMHO.....Red Line products are not needed for the vast majority of us everyday drivers and off-the-shelf stuff works just great (donning fire retardent sprayed asbestos underwear).