As you can see from my signature, I have a 2001 2.7L with 275K miles (444,000 km). If you go back a couple of years in the used oil analysis section you'll find my post where I did many used oil analysis on several different oils in this engine.
In a nutshell, with a decent quality conventional oil I suggest 3K - 3500 miles. Group III synthetics, perhaps 4500 to 5K miles max. I once ran Amsoil TSO 0W30 to 8K miles (13K km) in my engine and it was shot. It wasn't the TBN that was gone, but these engines cause faster than normal oxidation and nitration of the oil and that's what kills it. used oil analysis that simply analyze for wear metals but don't include oxidation/nitration/sulfation, don't tell the whole story.
If you do all city driving and/or short trip driving, I would shorten the intervals I've suggested.
