What weight oil is the best to use in the 5.0. Also what octane gas is the best.

87 octane is the recommended fuel for a Mark VII 5.0.
As far as oil that depends on climate, in MI I run straight 30W.
I don't know if anyone will agree with that, but it gives me the
most consistant oil pressure in my experience.

10/15 - 40
w/
89+ oct

Arizona Climate

Go ahead buddy, keep blowing your horn.......I'm reloading!

LOL man Im going to make that a sticker and put in on my back window, thats a good one :bowrofl:

The car is rated for 87 octane, so use it. Any more is blowing your money and actually hurting your engine more than helping. As for the oil, run what is listed for the engine. I can't remember, but I think it is 10W30.

Oil really depends on current/projected climate. If you're gonna be hitting sub-freezing temps, you want to go with 5w30. If it's going to be in a really hot climate, go with 10w40.