I participated in this survey (15 - 16 mpg city and 17 - 18 mpg hwy) a day or so after the poll was posted. I've been back several times since and noticed that the majority of the LLY owners fall into this category. I've been in the high 18's on several occasions, but didn't feel justified in voting in the 18 - 19 mpg class. Yesterday, on hwy #95 (just North of Las Vegas, NV) I ran a test under ideal conditions of road, wind, terrain, etc. and marked 20 miles at 70mph on the cruise control. The result was: 23.2 mpg according to my digital information center. My rig is a 2004.5 GMC C3500 CC, SLT, LB, 4WD D/A (LLY). After 6 mo. of use I now have 15K and the only thing I've been doing differently is using a fuel additive: Power Service -8 oz. per 25 gal. (states on the container: "absolutely no alcohol") Although this truck is running GREAT! I wasn't happy pulling a 36', 14+K, 5er over Baker grade (I-15 bet. Stateline, NV and Baker, CA) in 2nd gear, at 35mph at 3,500 rpm and both temp. gauges too close to hot for my comfort. Trips like that to San Diego resulted in 10mpg. Since my last trip, I've been anxious about the new Bank's set-up (in R&D for quite some time) for my LLY and got the GOOD NEWS call today: A six stage system (air filter, six-gun controller, exhaust system, boost and pyrometer gauges) that will selectively and progressively boost my engine/trans 128 HP and 345 fp torque. Stage #1 is the stock setting and every stage thereafter = a 20% boost. By going with the unique design of the Banks set-up, I think my engine/trans plus my 100,000 mi. after-market warranty will be better protected.