Canít comment on the V6, but my diesel Canyon is quite nice to tow our 21SS with and I averaged just over 13MPG during a 5,000+ mile road trip last summer which included going over a number of 11,000ft passes in Colorado and MT/WY.
Your fuel economy sounds about right for a gas truck, but you didnít say how fast you were towing. The difference between towing at 62-65MPH and 70MPH can be quite big in terms of fuel economy.
2017 GMC Canyon - CCLB, 4x4, 2.8L Duramax, ARE Z-series shell
2013 Shamrock 21SS