[MetroMPG]

Welcome! You're the first GM hybrid pickup owner I've met. One former neighbour had the Escalade hybrid -- same drivetrain technology if I'm not mistaken.

Anything you can do to reduce rolling and aerodynamic resistance will help the engine to go into cylinder shutdown mode sooner & longer. Do you have an easy way to monitor when it's in that mode -- a light on the dashboard?

Increasing tire pressure will help reduce rolling load, as Tim mentioned.

Anything you can do to reduce aerodynamic load will make a bigger difference. Did the truck come with those bars on the front end? Removing them would help. As would removing the running boards. (Also counts as weight reduction, which also helps... killing 2 birds.)

A tonneau will also help. An aero cap/aero shell will help even more!

Start a fuel log - start tracking your progress! And welcome to the forum.