I just moved from a 2012 xB with 88k miles on it to a 2013 xB with 47k miles on it. The newer xB isn't getting the mpg's I was getting with the 2012. The newer xB is getting about 2 mpg's less than the 2012 was. Same tires, air filter, engine etc. Not sure what oil weight it has in it since its new to me. Would 0w-20 vs. 10w-30 make that much difference? Has anyone had success squeezing a few more mpg's out of their xB, and if so, what did you do that made the difference?