Differential oil confusion; manual answers best!

[WHAMMO]

I've been reading a bunch of thread on what differential oil to use and everybody has a different answer it seems. I was about to simply buy Royal Purple without additive, but just found this might void warranty in some thread and cause a noisy rear end(from Corvette forums/ls1tech).

So I checked my manual and it gives a good answer to what to use;
Directly from a 13' SS owners's manual;

Page 11-13
*Rear Axle (SS);
-Rear Differential Fluid 75W-90 Limited Slip (GM Part No. 89021677 and
Friction Modifier 1052358, in Canada 89021678 and
Friction Modifier 992694).

Page 12-14
Rear Axle Fluid
V6 Engine 6–Speed Automatic 0.9 L 1.0 qt
V6 Engine 6–Speed Manual* 0.9 L 1.0 qt
V8 Engine* (L99 or LS3) 0.9 L 1.0 qt
V8 Engine (LSA) 2.0 L 2.1 qt

*Add 2.5 oz. (75 mL) of friction modifier to the specified quantity of axle lubricant.

^I noted that the 12' manual says 75ml of additive BUT the 13' says 98ml^ 98ml is a full small bottle. The part number is different from Can/USA too.

After reading this, if my warranty was over, I would get any synth 75W90 oil(heard Amsoil extreme is really great or Redline) WITH the additive.

FYI, from the GM dealer, the oil was pretty cheap; 16.89$/pint(cad$). Same as any other brand or so.

Another thing is when I asked the GM parts counter guy, he told me I would not need the additive, since its a full synthetic blend, which is FALSE; I showed him my manual! But its only needed for the SS/6-speed V6, not even on the LSA engines Camaro(ZL1)!

I'm gonna flush the oil tonight and see what it looks like after 5500km or so with a lot hard driving

I hope my rear end is gonna stay quiet as it sits right now.

Any opinion is welcome.

[IMG][/IMG]

link to 12' owners manual http://www.chevrolet.com/content/dam...2k12camaro.pdf