Check Engine Light?
 

My Check engine light came on about two weeks ago. Think it might have something to do with emissions.... I have heard from others that could impact my fe significantly. What's your take?

The CEL (Check Engine Light) in a modern car can mean any of thousands of possible malfunctions. A scan tool can pull the trouble codes which will identify approximately what the computer thinks is wrong. Mechanics, auto parts stores, and friends who have a ScanGauge can all pull your codes for you.

Once you know what codes are responsible for setting your CEL, you can begin asking what it might be about.

you can go to your local big box auto store and they will usually test it for you for free.

More often then not it will be an O2 sensor which will put a damper on your mileage. Other common problems are loose or a non sealing gas cap.

can a CEL ever increase your MPG?

My G/F's CEL was on, then off, many times, we finally took it to get it looked at. The diagnosis? She was putting too much gas in the car at fill up!!

If I remember correctly from other posts his Suburban is a 95. ScanGauge won't be much good to him, but there are other scantools he can use for it.