| Speed - | Air Resistance is responsible for about 1/2 of a trucks fuel costs at 55 MPH and below and Air resiatance related fuel costs quickly grow as speeds rise above 55 MPH - - to put it another way - overcoming air resistance takes about half of the energy a truck consumes at modest speeds much more dollars at higher speeds. Speed is the largest factor with air resistance because air resistance increases with the cube of the speed (speed x speed x speed). A rule of thumb - For each 1- MPH increase in speed above 55 MPH, fuel consumption goes up by about .1 MPG
cube math: 55 mph vs. 56,57 & 75 55x55x55= 166,375 56x56x56= 175,616 57x57x57= 185,193 75x75x75= 421,875 you can see that the number gets big, fast |
note; the web
is full of information to my brief thumb nails of comment. I will
attempt to provide some links to backup information. If you need info; good sites
are from the specific manufacturer of the product and the truck magazines with online
topic searches. The CCJ article below is an excellent example. a link ..maintenance issues relating to fuel mileage -
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| Acceleration and engine RPM– | Most diesel engines
have a fuel economy "sweet spot", an engine operating speed or
speed range that produces energy more efficiently than other revolutions
per minute (RPM).
In the recent past, this RPM sweet spot has generally been in the 1450-1550 RPM range. Since the 10-2002 EPA engines came out the sweet spot has drifted even lower for common engines. Cat' s have a 1325 RPM recommendation, Cummins sweet spot range is 1400-1450 RPM. When specing a truck, it is important to gear the truck so that the engine sweet spot and the average on highway vehicle speed matches up well.
the way When shifting through the lower gears it is often wise to shift to the next higher gear at or below these RPM’s. …"Idling up to speed" |
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| Cruise control - | Today’s electronically controlled engines will, in nearly every case be more efficient if the cruse control is on. | |
| Power – | A well tuned engine is much more efficient than one requiring service. While there are surely exceptions, more available "reserve" HP has proven again and again to be more efficient than less within engine displacement categories. With reserve power to overcome hills, wind resistance and the like while effortlessly accomplishing the flat land running a truck will be more efficient than one. The down side of more power is "hot-dogging", judicious use of extra power will save MPG. Being the first to the top of the hill will take away. | |
| Aerodynamics - | The easier it is for air to slip past the vehicle the lower the drag coefficient (this number, always less than 1 is multiplied by the speed cubed and a constant to determine horse power required to maintain a given speed) | |
| Idle time – | Idling can consumes as much as 1- 3 gallons of fuel per hour. During cold or hot weather, many truck drivers simply do not shut their engine off. If they drive 12 hours and idle 12 hours drivers can burn 12-36 gallons of daily fuel simply for comfort. A variety of systems are available to heat, cool or both during situations where a driver will traditionally idle the truck. Most of these systems offer quick paybacks as opposed to the idling alternative. Additionally, some localities are creating laws to ban truck idling. | |
| Braking | Excessive slowing down below cruise speed then accelerating to cruise speed | |
| De-acceleration | At highway exits, is it power on, then braking or gradual slow down as the exit approaches? | |
| Tire Pressure / alignments | Higher tire pressures equal lower rolling resistance. Tires in need of alignment, ...scuff. Scuff is the equivalent of pulling a tire down the road sideways. Shorter tire life and higher fuel cost is the result. | |
| Air System leaks | It takes power to run the air compressor. | |
| Fan Clutch | Is your fan running excessively? Is the clutch in proper adjustment? Are the fan shrouds in their place? |
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