Ok its been a long time since I have changed my diff fluid so long I don't remember much on what to do.
I wanted to know what is everyone using now as for fluid in the rear?
Are you using one that already has the LSD additives in it? If so which one?
How many quarts are you using?
Sorry guys its been a while and I can seem to find the answers I am looking for on google or on the forums

 

Unless it was replaced (i.e., upgraded), all S4 convertibles came with an open (non LSD) differential with 3.9 final drive ratio. You can use any API GL-5 75W-90 gear oil either petroleum based or synthetic. Fill capacity is specified as 1.4 quarts.

 

Mine has a s4 t2 diff in it when I got the car it had no diff. I was thinking about getting Lucas or Mobil 1 or Royal Purple

 

Mazda wants a SAE 90 GL-5 for that, 1.3 liters. 75-90 works great. factory fill was a mineral oil, but no downside to synthetic (slight increase in efficiency vs bigger cost)

 

Thank you for that. Knowing that the additive is needed with regular oil with the synthetic it says it has the additives in it. what do you think about that?

 

Last time I changed my gear oil, I used the Royal Purple Max Gear 75W-90. I have a clutch type LSD in my S5. I think RP already contains the additive. I haven't had any issues with this oil in its nearly 2 years of usage.

 

Perfect thank you for your help!