Schultz, I started splitting the difference on fill ups, too. Eventually I just left it at a happy medium. Changing the calibration on every tank made my feedback fluctuate too much (Oh, I'm doing crappy. Ooo, I'm doing good). Now, by leaving it alone, I get consistent feedback and it's off by much less at the next fill up.
Since you're seeing 155mpg during coasting I guess Barb's driving an automatic (those darn manual guys see 300+mpg while coasting!). I assume it's because of NC with the automatic transmission. My SG reports idle-fuel-consumption rates while NC, but the engine is running up to 1200rpm. I'm guessing it's using the rpm in its calc's, and that's throwing it off. More NC = more inaccuracy? Who knows? The truth in is in the pump.
