With 10,000 miles on my 2010 Freightliner Cascadia, it was definitely time to check the fuel mileage that I've averaged so far. Don't get me wrong, I check every tank full and constantly check the ECM display on the dash as it's accuracy matches my manual numbers to the nearest tenth. My life time fuel mileage on my old 2007 Freightliner Columbia was 5.8 mpg. For a car hauler, that's not too shabby because besides the truck itself, there are no aerodynamic advantages. For the Cascadia, I'm now getting 6.0 mpg. That's not as much as I wanted, however, I'll take an extra $1500 to $2000 a year! That's about how much the Cascadia will save me in fuel in my operation. That doesn't even count the decrease in maintenance costs due to the extended service schedule on the Detroit DD15 power plant! The fuel savings may not sound like much to you, but it has allowed me to shift budgeted fuel money into other categories like paying myself which is always good.
I think back to when I first started driving a slow company truck at the beginning of my career. I remember going from coast to coast and seeing the same few trucks pass me up to three and four times a day on the journey. I even told one of them on the CB that if I had a fast truck, I didn't think I would get anywhere! 
Anyway, on my recent trips to south Florida on the infamous I-95, I noticed it happening again. Except this time, I had a fast truck but I'm driving it like it's governed at 65 mph. I knew these drivers weren't in a hurry because they kept stopping at every truck stop on the way. Most were company trucks but some appeared to be owner-operators. From my experience, I can only conclude that they like throwing money away.