Recent 1200 Mile Trip

brplut40 · January 16, 2008

I recently took a trip from Eastern Nebraska to Washington, DC driving my truck (1998 GMC K1500 Z71 5.7L with dual exhaust 115,000 miles) with a 4 wheeler in the bed weighing around 500lbs and towing a double axle enclosed 6x12 u-haul trailer weighing around 3000lbs. I drove all Interstate and kept it around 65mph when I could. Since I have a wait4me tuned PCM I figured I would share my experience and gas mileage numbers.

Council Bluffs, IA to Iowa City, IA - 10.5mpg 89 octane with ethanol TUNED PCM, Flat terrain

Iowa City, IA to Champaign, IL -10.5mpg 87 octane TUNED PCM fairly flat

Champaign, IL to Indianapolis, IN - 12mpg 130 total miles 87 OCTANE TUNED PCM fairly flat, almost no downshifting

Indianapolis, IN to Columbus, OH - 12.2mpg 170 total miles 87 octane STOCK PCM, slight hills, some downshifting

Columbus, OH to Washington, PA - 10.7mpg 145 miles total 87 octane STOCK PCM, decent sized hills, downshifted a good amount

Washington, PA to Hagerstown, MD 11.32mpg 187 Miles total 87 octane TUNED PCM some 6% grades, in 3rd gear for over 50 of the 187 miles. Going 50mph up hills at 2500rpm.

With the tuned PCM going up hills the truck seems to have way more Torque. Going up some smaller, but long hills around 55mph, if you pedal it right the truck will not downshift, and will even slowly increase in speed. The truck holds overdrive longer and tends to not downshift as much. (I know, you probably shouldn't tow with the truck in overdrive) All around the truck just seems to have more power. I was shocked when I saw that I got 11.32mpg while going through the hills of Pennsylvania, West Virginia, and Maryland that I went through. You know they are big hills when there is always a far right lane for trucks and semis have their blinkers on. I can’t explain the poor mileage at the beginning of the trip, or why the tuned pcm did not get better gas mileage going across flatter terrain. I was just glad when I went from getting 10.7mpg with a good amount of hills to 11.32mpg with bigger hills and higher rpms.

I included the octane because I have heard that 89 octane with ethanol does not burn as efficient and will give you slightly lower gas mileage.