NOOB: My Scangauge is way off suddenly.
 

So when I first plugged it in, I set the engine size, fuel tank size, and wheel size compensation (3%). I finished the 3/4 tank I had in the car with approx 42mpg on the avg... which sounded great.

Sure enough my mileage for that full tank was 38mpg, so I was sure the gauge would be closer now. I filled it up from E till the pump stopped automatically. It was at 10.008 gallons out of my maximum of 12. I hit the REFILL button, and I cant remember if I hit save or not.

Ever since then, I'm getting readings that show an average of 20mpg at the best, though the dashboard gauge is consistent with my 38mpg tanks progress.

So I've used about 1/8 tank... how do I get it back in the neighborhood of realistic mpg calculations?

Just a followup that might help someone out...

I was able to get my Scangauge back to a more realistic setting by doing this:

1. Fill up the tank, then select HOME>MORE>FILLUP and Save.
   
2. Then drive it for a quarter tank like that, and go fill it up again.
   
3. At this point the FILLUP screen will be telling you what it thinks you have used since the last fillup. Use the top buttons to adjust that amount to what is indicated on the pump from your fillup.
   
4. Now hit SAVE and you're good to go.
   
5. Try to use the same station and same pump every time and you're readings will be more accurate.

Make sure the SG didn't reset itself accidentally -- it will go back to the default 3.0L engine and cause some really low numbers.

RH77

Oh, I'll look at that, too. Thanks!