Good idea. Added to my list. I also tighten this to just snug. The o-ring keeps the oil where it's supposed to be.@Amaruq
Not mandatory, but a 3.6 owner that is doing his/her own oil changes, probably should have one of these on the garage shelf all the time.
The cap is known to crack so, it is cheap cheap insurance ($15.00) to have one on hand.
--A month or so ago, I even had a local tech call and ask me if he could have my new spare cap as he could not get one right away and he had cracked a cap on a clients Jeep. The tech knew I kept a spare as we talk/brain storm pretty often. He borrowed and replaced it with a new one a week later.