Originally Posted by Dyno Don
Without having Ford spec fluids in the differential, you have 0% chance of having any warranty claims honored for the rear end & associated parts.
Hi, Don. My warranty is really up anyhow. I did some research long ago on lubricants and Mobil 1 was possibly the best. All synthetics are not the same, I just used Royal Purple because it came with some other stuff I ordered. I won't use it again. Mobil 1 also makes a full synthetic ATF which our Mustangs use in the manual trans case. When I owned the '07 GT/CS I used M1 and immediately the car shifted easier and quieter. Not cheap stuff, but most good things cost a few bucks.