If you bought a Scan Gauge II - be sure to change the engine type to HYBRID or the unit will time out, as I found out the hard way - its in the book but who reads the book....

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My SG2 shutoff at the first stoplight which reminded me to set the fuel type.

I set the speed correction to 3% and now my GPS and the SG2 match as far as current speed is concerned. Trip distance is still slightly off but not as much as before the correction.

 

Driving in this morning (playing with this thing in the rain at 70 MPH), I tried 1, 2, and 3% comparing it to my hand-held Garmin GPS that I deem very reliable. At 70 MPH it seemed to match pretty good at 3%. The GPS shows in tenths and rounding the number was matching pretty good.

At 40 - 60 MPH, I found that it was a little high and that 2% was a better choice. At 20 - 40 MPH the 2% seemed ideal as well.

It may be the air in my tires or other factors, but 2% seems to be my choice.