I have 160,000 on my 5.0 Mustang, and it runs quicker now than it did with 70,000.
Will be replacing engine, transmission, rear end,brakes, and suspension soon anyway though...(performance reasons)
I drive it everyday like I stole it, but I take care of all the maintenance exactly when it needs it. I've never had it not start, I've never been stranded, its been 10000000% reliable.
I've used way too many different brands of oil... from Valvoline synthetic, to Castrol synthetic, to AMsoil, to Mobil.....
I've currently decided to stay with Mobil1 15w50.