well i was looking around town for royal purple for my tranny and diff. well the only thing that i can find is 75w-140 will that work for my car. its and S4 GXL thanks. and what about mobile 1 75w-90. The royal purple does comes with LSD additive right and also is the mobile 1 too. thanks.

 

75W140 is too thick for a FC rear end

The Mobil1 is okay if you can keep the temp down. Its high sufate content, tends to break down at around 225F whcih can cause problems with the syncros in the FC tranny

 

so then 75w-90 fluid will work just fine right or do i only have to put 80w-90 in the car.

 

I have used 75W90 but what is best is either Redline, Royal Purple, Neo Synthetics in the correct weight, or straight 90W unnless you are seeing below freezing temps.

 

ohh ok because i have been looking around town and only find royal purple in 75w-140. theres other like mobile one but i dont think mobile one is that good.will the 75-140 work good.