Does anyone know if the Mobil 1 Synthetic differential lube has the posi additive added already? I looked at a bottle of it at a local parts store and it gave me the impression that it did, but it didn't come out and clearly state so. If someone knows the answer to this, I would greatly appreciate hearing from you.

I did a search on this site, but didn't find a definitive answer.

Thanks,

Marty

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X77, Stock matching number 302, 4:10 rear, black int, weld prostars, 2.5" Flowmaster 50 Series

http://community.webshots.com/user/lakemg

I just emailed Mobil 1 to see what they say. If I don't hear from anyone on this site, I'll post my learnings from Mobil, if/when they reply to my question.

Thanks...

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X77, Stock matching number 302, 4:10 rear, black int, weld prostars, 2.5" Flowmaster 50 Series

http://community.webshots.com/user/lakemg

I recommend using the oil without the additive first. If it pops then you should put in the additive. If you can stand it without the additive your posi will lock up better. The additive makes it easier for the clutches to slip, which kind of defeats the purpose of having a limited slip differential in the first place.

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'69 RS/SS396 pro street
427/4spd/9"
Byars Performance
High Performance Drive Train Parts And Service
www.lubedealer.com/biggearhead (http://www.lubedealer.com/biggearhead)

HI just wanted to give my input on your question on mobil one rear diff. oil.A few years ago I used the moil one in my 12-bolt I have in my nova and it chattered pretty good when turning around corners so I drained it out and put in the gm rear gear fluid with a small bottle of the additive and it's been quiet ever since. At the time I worked at a corvette restoration shop and mobil one is what they seem to put in everything but it didn't seem to work in my car. Joe

I recently changed the differential fluid in my 12 bolt and I went with Mobil 1 and one bottle of GM additive. No chattering here. Don't know if it is the bottle of additive that made the difference between my car and Joe's, but just thought I'd share.

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Donald
68 Camaro convertible (L30/M20, L48, or neither?) (http://www.dre-si.com/68ss)

Hey guys thanks for all of the helpful replies. I finally got word back from Mobil and this is what they said:

"If your owner's manual requires an GM additive it must be
added with the Mobil1 product to ensure proper usage."