OK, I feel bad in case this was a legitimate question.

Check you owner's manual. It probably says "lifetime fill", I don't know, I haven't checked. I recommend changing the oil on the REAR differential every 75,000-125,000 miles, based dramatically on driving conditions. Frequent racing may require more frequent changes. You can't change the oil on the front differential, because there isn't one. The Crossfire is not all wheel drive.