I'm with you, with my '97 ext. cab 4x4 Chevy w/ 3.73, 5.7, & auto I was able to get anywhere from 17 - 19. With my '99 Silverado equipped the same way except for a 5.3 I'm able to go anywhere from 18 - 20 (21 a couple of times) and yes all were manually calculated. I don't usually complain about the MPG of my Chevies (Silverado & Trailblazer) they are both big vehicles and don't do exceptional, but for what they are I think they do pretty good. But at the same time I use our Honda Accord as my commuter vehicle (54 miles each way) as it gets between 30 & 33 MPG. Plus it is a lot cheaper vehicle to replace than either the Silverado or the Trailblazer.