Just because they raise sppeed limits to 80 does'nt mean you ahve to drive them. I ran a Peterbilt with a 500 HP CAT and 15 spd overdrive from Baltimore to Seattle. I ran 75 when I could from ID to IA and averaged 6 MPG westbound and 7 east bound over a4 year period. Schneider trucking argues that 62 is ideal but if you figure 13 MPH 10 hrs aday, that's 130 miles X 39000 mi X 4 yr thats 156 K X $2/mile and I made more money, had more home time and drove a Large Car instead of a Pumpkin, stripped to bare essentials and trade in value was double.