I like the concept of the "driving activity" and "smart driver" functions of the My Buick app but sadly, the data presented there is often incomplete or inaccurate. I made a 300 mile round trip journey Thursday and the app shows my fuel economy for the day as 19 mpg. When looking at the details of each trip for the day, some of the fuel economy figures are reported as -- which I assume are interpreted as "0" when calculating the overall fuel economy for the day. I have no idea why the fuel economy was not calculated. Is this a common issue or is it just my issue? If it's common, I don't think I would pay for this service from OnStar unless the data presented is consistently accurate. I haven't noticed this issue on past trips - mpg usually shows 30-32 mpg average on highway trips.