Need advice on CEL light

[ryanwise]

This is probably a question without a real answer but I thought I would tap the vast knowledge of this forum before I take action. Maybe somebody has had this experience and can point me in the right direction. I just did a DE at Sebring last weekend. The car handled flawlessly. On the way back home to Tampa, the CEL light came on. The car continued to run fine and you would have never known anything was wrong. While I had not used the computer to check MPG , I had noticed the car seemed to be using a little more fuel the past few months before this past weekend. I know since I have owned the car for the last 4 years, at 70mph, the computer was showing about 27+mpg and once the CEL came on and I reset the computer, I was reading about 23.5mpg. So , I have a CEL and Im losing MPG. The question is............do you think I should spring for a code reader and try to make the diagnosis myself and relay the info back to the forum for a self fix, or just take it to the dealer.