First post here, but I've been using a fuel-efficient driving style for many years.
Here's my question: my check-engine light just came on yesterday and I was wondering if this is a good time for me to buy a ScanGauge? What are the chances it will save me some money just to see why my check-engine light is on?
Last time the light came on it was an air-sensor that needed to be replaced for about $400.
Don't buy the ScanGauge for the code; you can get scanners a lot cheaper ($40 at Harbor Freight, for example), and as Erik mentioned, you can probably get it scanned for free anyway. Do get the SG to help you refine your style if you want to.