My brother and I replaced the mobil 1 gear oil in his transmission with royal purple and it shifted way better. Stopped the small grind into 3rd. The mobil 1 only had 4k miles on it, it wasn't worn out.
I've been using Royal Purple for about 1 year in the Taurus and 8 months in the SVT Contour. The Taurus had Mobil 1 before that as did the Contour. The Contour has Royal Purple manual trans oil as well.
I have no complaints about the products at all. Both car perform great, and I have peace of mind knowing the product's abilties far exceed the stresses inflicted by my driving style.
The Contour shifts great. There was a noticeable, albeit negligible, increase in power with the Contour, first when I replaced the engine oil and again when I replaced the trans oil. The Taurus didn't show any noticealbe difference. I plan to replace the power steering oil with Royal Purple in both cars eventually.
We first used Royal Purple in a friends '03 Cobra. He dynoed before and after and gained about 10hp after changing all oils to Royal Purple. That was enough to convince me.
I'm able to purchase Royal Purple at a discount and tax free through the PX (Army base store). I have a case sitting in the garage right now... both cars are due for a transfusion....
There is a supplier on eBay that sells 5 gallon mini-barrels for about $97 and shipping is free. That comes out to about $4.85 a quart. As much as I use, I will probably purchase from this seller in the future.