I have a G56 with 3.73's and get terrible mileage. At 70 the truck is over 2k RPM with 33" tires. Think average of 13-15 between 70 and 80 unloaded, interstate. Pulling a 28', weighing maybe 8k, enclosed I averaged 8.5 at 75.
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2007 6.7 2500 Crew Cab 6 Speed Manual. Black, Black Rockstars, STTs, H&S 4", MBRP, PMT, AFE Valair DD.
Chrome wont get you home and money wont buy you a
Road Armor.