2012 JSW 2.0 TDI fuel economy

Hi guys, just bought a 2012 TDI last night. Took it to work for its first highway road trip. Previously had a 14’ that had issues with intercooler and DPF, so I got out of that car and into this. The 2012 has 29k Miles on it. The 2014 I took on a trip and averaged 42 mpg at 70-75 mph. The 2012 I drove today seemed a little lackluster, I’m averaging 34.3 on all highway driving at the same speeds? Any reason for such a difference? Both cars are JSW, this 2012 is CPO from local VW dealer in NJ. Looking for some feedback to what you guys see fuel economy wise out of a 2012, I would appreciate the input as I’d like to find out if I have a fuel system problem? Many thanks!