Peak rpm range is 1200 to 1500. Torque is higher at lower rpm and is more effective at pulling than horse power.
Tire Tread and Brand
Below 50 mph, tires make the biggest difference in driving mpg.
Half tread (worn) tires are approx 6% better on mpg than full tread (new) tires.
Ribbed tires are 2-4% better on fuel economy than lugged tires.
Every 10 psi under 100 that a truck's tires are under-inflated reduces fuel economy by 1%.
Fuel efficient tire brands can improve fuel efficiency by as much as .5 mpg.
CRE has found Michelin 275-80R-22.5 XDA energy for the Drives, and XZA3 for the steers are the most fuel efficient tires.
Tire condition and inflation is just as important on trailer tires as it is on tractor tires.
An engine geared to run 1450 rpm at 65 mph gets approx 4% better mpg than one geared to run 1600 rpm at 65 mph.
The optimal transmission gearing is 9-speed.
Over the road regeneration uses approx 1 gallon of fuel, while parked regeneration uses approx 3 gallons of fuel.
When the dash light indicates a regeneration is needed while the truck is idling, Drivers should try to change duty status if possible so they're on the road when regeneration occurs.
Bio-diesel fuels will increase the number of regenerations required. Bio-diesel also generates less power and offers lower mpg.
Proper Driving Practices
Engines use up to one full gallon of fuel per hour while idling.
At 70% idle, a trucks overall fuel economy is reduced by almost one fifth, or approx one full mpg.
Modern engines do not require warm up periods. You can drive up to 70% throttle as soon as oil pressure is up. Drivers should shut off the truck when not in the cab.
Modern engines do not require long cool down periods. A 3 minute idle after stopping is sufficient to cool down the engine prior to shut off. Drivers should shut off the truck when not in the cab.
Bunk heaters are provided to eliminate the need for idling when outside air temperature is between 20 and 70 degrees.
If idling up is necessary for air conditioning or for extended idle, you should not exceed 900 RPM.
Smooth Acceleration and Braking
Suggestions for smooth operation include anticipating changes in traffic and road conditions, avoid abrupt stops or rapid changes in vehicle speed, and minimize use of service brakes by planning ahead.
Braking not only costs fuel economy because you're losing momentum, but also because you're activating an accessory that draws power -- the air compressor.
Each stop costs approx one third of a gallon to return to speed.
Drivers should consolidate stops for food, fuel, showers, maintenance, pre-trips, and personal needs to reduce fuel expense.
Top Gear Cruising
One gear down decreases mpg by approx 16% due to gear mesh effect.
A 20% difference in time spent in top gear could result in as much as a 4% difference in fuel economy.
Out Of Route
Stay on route. Each out of route miles costs $.73 in fuel alone at $4.00 per gallon.
Ensure all regularly scheduled maintenance services are completed. Poor fuel economy could be equipment related.