No matter the truck, owned or not, I would not drive it over 65 anyway. The extra mile per gallon I could get by driving slower would put about $10K extra in my pocket with the current price for fuel.
I personnaly run around 60 most of the time and ALWAYS get my loads where they need to be on time. With less stress and more relaxed. I average over 7mpg. With the industry standard of 6mpg, I am keeping $10K more in my pocket at the end of the year. Most of my loads deliver by appt, so getting there sooner is stupid.
That being said. Look... anyone who has been in trucking very long knows that profit margins in trucking companies are pretty slim. And fuel is the largest cost after the driver pay. Therefore, fuel costs have to be kept manageable. The only way the companies can do this is negotiate fuel discounts by using a network and cutting the truck speed down. If you can come up with a better way.... let them know. Also, insurance costs are getting way out of line and the companies can get cheaper rates by keeping the trucks governed down. Sorry, but money is the driving factor in all this. Sure, I'll bet your company would let you run faster if you sacrifice 5 or more cents per mile in pay back to them.
Even as a company driver, their are benefits. Less stress, not worrying about the "bears", etc. Just kick back at 60-65, listen to the XM radio and relax. Doing this, I am still able to legally average around 3000 miles a week and be by the house once or twice during the week, and be home on the weekends. Not all stressed out from the week's driving. It makes sense for a O/O to do the same. Have these same benefits and extra money to take home (that is if they are getting the proper fuel surcharge... another issue).
If you want to go fast, go get some sponsers and get into NASCAR. lot more fun than delivering freight and you can get your picture on tv.