devinv Report post Posted July 11, 2007 6.0 is a gas guzzler in general, maybe not as bad in a 1500 like the ss, but in a 2500 yeah. I had an '03 ext silverado with a aftermarket cam, exhaust, intake, corvette servos, 3k stall, etc. With 22 inch wheels and got 10 to 11 mpg. I now have an '03 ext cab sierra with 5.3 engine with 7 inch suspension and 3 inch body with 37s, exhaust, intake, 4.11 gears, and programmed. I get 14 in the city. Bigger engine pulls the weight of the truck better without stress. But as stated above, I think tires make a huge difference too. I was running nitto mud grapplers and got 11 in the city at best, not I have discoverer stt's and get 14. Share this post Link to post Share on other sites
hunterdude Report post Posted July 14, 2007 I have a 01 HD and in town I will usually only get around 11, and if I don't hammer it to hard on the highway I can get 13. The 6.0 is a gas hog but for a gasser it will run pretty good. I put a throttle body spacer on it and noticed more power in the low end and mid range. Next will be a Magna flow muffler. I have 285's mt/r 's . Share this post Link to post Share on other sites
