I have a trailblazer with about 47,000 miles on it. 4.1 vortec engine. I average about 17 to 19 mpg. any tips on raising that?

Sounds about right....Maybe put a K+N panel air filter in it, you might see .5 mpg better but no miracles. It'll run stronger when towing/pulling hills.

Run the max reccomended air pressure stamped on the sidewall of the tire, rather than what the GM data says...