Im sure there's 100 threads here about all sorts of fluids, but rather than scavenging for information that leaves me questioning, I'd like to address them all here.

What is everyone using for Engine Oil, Coolant, Transmission Fluid, Differential Oil, Fuel Additives, and anything else? And why? Who gets the best deals from where? What makes one fluid/brand better than another? If Im missing any other obvious questions, please tell me!