you have a 2.5i. It really isn't going to matter all that much. Just stick with an OEM weight oil and pick one. Everyone here hates mobile 1 so don't get that just so you conform to your peers.
I use castrol synthetic 10w30. Prior to that, pennzoil synthetic and dyno. Doesn't make a difference. And for someone to use something like 40 weight oil is silly. I installed an oil pressure gauge and I was a little surprised at how much pressure these motors have. Full warm, anything above idle I see at least 80psi. And obviously cold it's well over 100psi (don't actually know because the gauge stops at 100psi). I will be switching to 5w-30 next change.