I believe the factory recommends 5-30w, what I've always done on my daily drivers and summer toys is after the first 500-750 miles change the oil with the high quality oil of your choice, not synthetic, run another 750 to 1000 miles any swap to synthetic, I like Mobil one but Royal Purple, Red line and a host of others offer quality synthetics. If you building a high performance motor, add another 2 oil changes, one after the first 10 minutes of run in, and another at the 50-100 mile range, again do not break in a motor with synthetics. This procedure has served me well from a 4 cylinder, 120hp Ranger to a 800hp Chevelle, I have yet to toss a motor.
Since my dealer service dept. keeps banker's hours, I just went to Lube Center at 3K miles and got an oil change with 5W-30 Penzoil - the 4.7L is a bit of an older design - I'm thinking I'm just going to stick with conventional oil.
I buy Molil 1 at Costco for 26.00 a six pack and my dealer charges me 19.95 for a filter and labor, so lets say it's 50.00 every three thousand miles. I like the fact that if I stretch it to 4 thousand I have that additional protection. Mobil also just released a 5000 mile synthetic and a Truck and SUV synthetic, I believe the long life synthetic would be very cost effective, you figure you would be doing two standard oil changes to one synthetic so cost wise it should be a wash and you get the extra protection.
I don't personally buy into the whole 3000 mile oil change theory (unless you're towing or driving under extremelly demanding conditions)...I did it for this car because it's new (safety for break-in, etc) but cars equipped with on-board oil analyzers quite often indicate standard motor oils can last from 6K to 12K miles. The majority of my driving is highway - I'll probably stick with the schedule A in the long run. I've driven 5 previous vehicles into the ground (most with 200K miles and up) and the engines were never the ultimate failure mode.
For all I know you may be right on the 3K theory, I've always run Mobil 1 thats what works for me, my thought always was if it's good enough for every Porsche that leaves the factory than its good enough for me, do I think synthetics are better than conventional oil, yes, it's been proven, but there are plenty of people than run standard oil with no ill effects, I just like knowing I have the extra protection.
My Commander is not a daily driver so I might put on 5000 miles a year, I could see where it would get old dropping $50.00 a month for oil changes. I don't put synthetic in my company car and I've yet to blown it up (god knows I've tried) as long as you do regular oil changes I'm sure you'll be fine.
I run mobil one 5w-20 just like the good book says. Personally, I think this is a bit thin, but it is what is reccomended.
As for the whole 3000 mile change thing, just how dirty your oil becomes should be a strong factor when deciding to change it. Keep the air filter CLEAN, blow it off with an air hose from time to time. A rechargable K&N works great. I drove a 4.7gc for five years before i sold it. Ran 20w50 mobil 1 and kept the air filter clean. had oil changed at 5000 mi intervals. Never a hiccup!