Usage:
3176, 3306, 3406 Truck Engines
Fuel mileage on heavy duty trucks can vary significantly depending on the ambient (outside air) temperature. On the average, the tank mileage (mpg) will decrease by several tenths of a mile per gallon in the winter and in some extreme cases a noticeable loss in power will also be observed. Only a small portion of these changes are related to the engine itself.
It has always been assumed that engines actually run better in cool or colder weather. This is true in most cases because of cooler inlet air and denser fuel. With these cold weather conditions, the engine will actually have a slightly increased flywheel horsepower. The problem lies in the increase in horsepower required to move the vehicle down the road in cold weather. Some of these factors are the denser air that the vehicle is moving through, rolling resistance of the tires and the increased friction in the drive train and wheel bearings. This change does not happen suddenly, but in a very predictable manner with temperature fluctuations.
Fuel consumption testing recently completed compared several different truck configurations to a control truck over a period of time from late summer to mid winter. The different truck configurations were compared to the control truck which had no modifications made during the testing. The tests were all run on the same 180 mile (round trip) stretch of interstate. Each of the 90 mile (one way) legs of the trip were completed within ± 15 seconds unless traffic became a problem.
The ambient temperature on these runs varied from 28°F to 90°F. Winds varied from calm to in excess of 25 mph from different directions. The tank mileage (mpg) was plotted against ambient temperature for each run made. A best fit line was drawn through the data shown in the graph. The overall temperature effect on tank mileage (mpg) was two percent reduction for every ten degree drop in temperature. At any given temperature, the tank mileage could vary ± 1/2mpg due to wind velocity and direction.
During the tests, it was observed that the tank mileage (mpg) would actually decrease at night as a result of the decrease in ambient temperature.
For example, the ambient temperature was 80°F on one trip and 30°F on another trip. On the 80 degree day the truck averaged 6.5 mpg and on the 30 degree day the truck averaged 5.85 mpg.
In addition, if a truck is put into service in the fall or winter, it has no warm weather history to show it's actual capability for several months. This can lead to customer dissatisfaction until the weather warms and the tank mileage (mpg) improves.
