1 Census 2010 Race for Effingham County, Illinois. 2  Census 2010 Latino for Effingham County, Illinois. 3  Census 2000 Race for Effingham County, Illinois. 4  Census 2000 Latino for Effingham County, Illinois.  Illinois Voters for Effingham County, Illinois.
On average, a truck traveling at 65 mph instead of 75 mph will experience up to 27-percent improvement in fuel consumption. As a rule of thumb, for every one mile per hour increase in speed, there is a corresponding 0.14 mile-per-gallon (mpg) fuel consumption penalty, says Kedzie.
In 1973, the feds estimated that semis got about 5.6 miles per gallon of diesel; today's estimate is 6.5 mpg, although different trucks get fuel economy in a range from 4 to 8. Going up a steep hill, a truck's mileage might drop to about 2.9 mpg, while going down the same hill will raise it to more than 23 mpg. New fuel-economy standards that take effect beginning in 2014 will require semi trucks with a sleeper cab to get 7.2 mpg on level roads.