is there a way to improve gas mileage? tuners that work. 2008 trailblazer 4.2. Thank you.

 

Not really other than the usual things, run all 4 tires at 35-36 lbs. Make sure air filter is clean or change air filter . Run a quality fuel system cleaner thru the system once per oil change . You will never get more than 22-23 mpg highway on these in the summer . It will be lower than that in the winter .