I purchased our 2014 Cruze diesel brand new from a local dealership. Everything was great until the vehicle O2 sensor recall/recalibration was done with under 10k on the vehicle. Since then, my mileage dropped significantly(averaging between 18-20mpg, with full tank range consistently indicating less than 350 miles). I also experienced a significant loss in power and driveability, with the vehicle lagging upon acceleration, and intermittent shifting issues. I have had it into the dealership several times, and they have repeatedly told me they can find nothing wrong. They also told me the poor mileage sometimes just happens! I am thoroughly frustrated with the situation, as the vehicle still has under 50k on it, and I really like(d) the power and mileage the vehicle had when I first bought it. Any feedback or suggestions on a remedy are greatly appreciated, and if I can’t find an answer I’m likely going to use it as a trade in on another vehicle before I start having costly repair bills to keep it on the road!