If it matters I have two 4.6l Mod cars; A 95 T-bird and a 95 Cougar. The bird I've had since 97, purchased with 40K miles on it ford brand dino since day1. I put Mobil 1 from purchase to 100K miles typically using .5 quart oil/3000 mi. I then switched to Motrlube 10-40 and my consumption is down to 0 at a 10k change . The Cougar I purchased last October with 87K miles. Previous owner used dino, what ever was avail, I guess. Engine used 1 quart/ 3000 miles. Switched to Motrlube 10-40. 97k on the odo, consumption down to less than .25 quart for 9k miles. My cousin(who works at ford in VA) said that 4.6 mods from 91-94 had an oil pump design that could have difficulty with thicker oils, (especially dinos and especially if you're down .5 quart or more) at startup. This was changed to a better design in 94-95, so this should not be an issue for a 95 and up properly maintained engine(but you still wouldn't use higher than 10-40). Unfortunately, on the cougar I think the previous owner was less than timely on changing the oil so there is a bit more usage. Hope this helps.
Cheers,
Dennis