Looking at fuilds since I want to change mine soon. I did some research to compare them. The reading I have done, some have talked about the PTU getting to hot and the oils reaching their flash points. Some say the heat just breaks them down. And with it being 13 deg F yesterday here in indy, cold 75w-140 is thick. So the viscosity at different temps comes in to play as well. I have listed a 5 different companies flash points and the viscosity measurements(d445 test). All numbers came from the company websites. Not an independent. Companies like redline and amsoil make great stuff but are hard to find. Royal purple can be too. Here in the indy aera Lucas stuff is easy to find. And mobil one is everywhere. I listed the ford stuff since our cars came with it from the factory. The NS line from redline has the least amount of friction modifiers. But the flash point is real close to operrating temp. So I wouldn't recommend them. (Warning, Im no expert) And since the 2013 SHO manual listed 80W-90 recommend for the rear I listed it as well. When it comes to the viscosity numbers the smaller difference between the 2 numbers is what you want. Means there is less of a change in viscosity. Couldn't find the second viscosity number for the ford fuilds. Ps the pic was taken with my forward facing camera. The shadow up top is my face holding up the paper so I can see the phone for the pic.