I am using Mobil1 5w20 with Mobil1 filter every 8,000 - 10,000km. Thats the weight recommended for the 5.7, so I'm not sure what weight is recommended for the 3.6
My oil change chime comes on every 4,000km, and I haven't been able to figure out how to change it to ring at 8,000 so after the first chime, I reset it and then after the 2nd chime, I get the oil change done.
The only thing is it must be 5W-20 or the camshaft phasers won't work properly. Most of us use one type of synthetic or another, only a few are still using dino oil. The Pentastar uses 6 quarts with filter--don't use a FRAM whatever you do, try a better brand like WIX /Bosch/etc--no cheap ones.
Older 3.6 recommended oil is 5W-30, at least through '12 or '13. Should be printed on the filler cap if the manual isn't handy. Recommended interval is no more than 8K miles/1275 km. But you will see that oil is like politics and religion around here. Fortunately, people post actual results from used oil analysis so you can see how things stack up. Using a quality filter is a good idea no matter what you do.