Got ahead of myself. Plug in your SG, then fill up the tank but don't make any adjustments for that FIRST TANK. The next time you refill, wait until you have 1/4 left in the tank and then you can make your fillup adjustments. Adjustments at the fillup are based on the ACTUAL amount of fuel I pumped into the tank at that time so no need for traditional tracking.
ex:
I pumped in 8.747 gallons today. I turn on the Scangauge, go to FILLUP and it says I used 8.6 gallons. I then adjust it to agree with the actual fill amount (8.7) and note the adjustment percentage (+13.3%). That's it.
When you first plug in the SG, you need to calibrate your car info such as engine size, tank size, fuel type and car type. The instructions for the installation are pretty clear.
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Your Cav should have DFCO. What you do will depend on what you need to do -- if you need to stop soon, I'd coast in gear. If you have a downslope or no stops in the near future, neutral is better. This is where having a SG is really useful but it sounds like you already know what you're doing.
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I still use traditional tracking of odometer difference and tank amounts to determine my ACTUAL mpg (plus I use that to plug into the [garage]) because the SG is not perfect when it comes to tank calculations. It's close but I rely on it for instant feedback on the road.
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Don't worry about messing it up.
