[tbear853]

I've been using my SGII on a 1995 Thunderbird (Ford had OBDII on 94/95 T-Birds and Cats), a 2001 Mercury Grand Marquis, a '2007 F150 FX4, and starting this past June, a 2008 Mustang GT (all with dedicated cords and velcro). Occasionally I'll slip it on my wife's '03 Forester.

I tried that calibrating when I first got it, way back in 2010 .... but seems to me I was just calibrating it to fuel tank size. Maybe it was calculating based on AFR / O2 sensor readings? Anyway, I haven't calibrated it since 2010 in any case.

I religiously figure my MPG fill to fill using math and I keep the SGII left side X-gages set to MPG instant above MPG average, and I find that when I drive without shutting off (so no resetting) from fill to fill like one may see on road trips (love road trips) so the SGII has it all .... the SGII average reading is nearly always within a tenth or two of what math tells me.

I know it knows "time", it get's a distance from speed devided by time, I didn't know for sure where it got gallons per hour, but appearantly it get's a pretty good sense from whatever my Fords tell it? I do know by using radar (30+ years LEO) in the past and by timing over mile posts multiple times that with OEM tire sizes, my veh's have pretty accurate odo/speedometers.

I use the instant MPG like a vacuum gage of old, which I still use on my '77 F150. It's good to train one to anticipate stops / slowdowns / hills, etc to maximize the average. It's almost like a video game .... I have favorite stations and I find myself trying to beat my normal average from fill up (reset) to home.