Brand new 2022 Cascadia DD15 gets bad fuel economy

I bought a brand new Cascadia MY 2022 6 months ago. I drive on mostly flat ground in the midwest, with little crosswinds, and midweight loads in a dryvan, and I have been averaging barely 7mpg, never getting any better than that. I drive efficiently (62mph, gentle acceleration etc) and still get awful fuel economy. I get no check engine lights or error codes, and the dealer doesn't want to do anything to help me. Most O/Os in the company I work at get at least 8mpg or better in their new Cascadias.

 

I have a 2.85 axle ratio, automatic transmission, and I do not idle. It does consume more oil than I'd like but I don't know if that has anything to do with the fuel economy. Also according to a compression test some cylinders are at 100% but there is one with 91% and another at 93%. Again, don't know if that affects fuel consumption.

 

I'm past 50 000 miles or a break in period so it can't be related to that.

 

I'm always pulling different trailers so it can't be a trailer related issue.