I have broken the 10,000 mile mark with my 07 LMM. I have not noticed any increase in mileage yet. I average 17mpg hwy and, sadly, about 10.5 in town. This is with very light footed driving also. The 10.5 in town is with the computer set to the factory settings (Bully Dog progammer). I just filled up with my first tank of B50, I'll use B99 when the weather warms, and reset the programmer to the next power setting. Speaking with the service manager at my Chevy dealership, they have had problems with the programmers causing the dpf's to clog, so I have left mine at the stock setting. With my '03 Duramax, I ran B99 often and found that there was much less soot produced with that fuel, so I'm testing to see if the combination of the programmer and the Bio-Diesel will result in improved economy. I will report back after a month or running this scenario.

On a separate note, I find that my computer is generally off by one gallon at fill ups compared to the amount of fuel that it takes to fill the tank. I attribute this to the remote start that I use every morning to take the ice off. I don't think the computer monitors the fuel usage while in the remote start mode.