I’ve got a 23 LZO. Depending on how much skinny pedal I used I averaged 22-24 mpg in the city and 28-32 on the highway. Leveled with 35s now and took off some mpg. Check engine light came on a few times after I put DEF in it but it went away after a few miles and hasn’t been back on. Only issue I had so far. Honestly love the diesel over the 2014 5.3 I had before