IMPROVING YOUR BOTTOM LINE
through fuel economy
Optimizing fuel economy, performance and engine life is a goal of any transportation manager. Peterson is here to help you improve your fuel economy, save money, and improve your fuel mileage by following these 4 recommendations:
1. Slow Down – Do not exceed 60 mph. This can be implemented immediately and does not require up front capital investments. It is likely to be the driver's most effective cost saving action.
2. Spec Smart – For your next purchase, consider a tractor/trailer with good aerodynamic characteristics and low rolling resistance tires.
3. Don't Idle – Do not run the engine at idle more than absolutely necessary.
4. Driver Training – You will learn proper operating habits that will save money on fuel, tires, brakes, and tractor/trailer maintenance. A safe driver is also rewarded with a more enjoyable driving experience.
Learn more about helping your fuel economy and vehicle performance, listed here are the top 10 things that hurt fuel economy:
The most significant fuel economy variable is the driver. It is the driver who controls the vehicle speed, trailer gap setting, acceleration rate, brake usage, idle time, tire inflation pressure, shifting technique and more. It is not uncommon for fleets with identically spec'ed trucks to see as much as 25% (5.0 vs 6.7 mpg) in fuel consumption difference between the least effective and the most effective drivers.
2. Interstate Vs. Congested roads
Avoid operating in congested areas whenever possible. 15% of the miles traveled on congested roads translate into a 7% fuel economy penalty. 25% of the miles traveled on congested roads are equivalent to a 14% fuel economy penalty.
3. Vehicle Speed
Vehicle speed is another very important factor affecting fuel economy. The rule of thumb to remember is that fuel economy will change approximately 0.1 mpg for every 1 mph speed change above 55 mph. In other words, decreasing vehicle speed from 70 mph to 65 mph can improve fuel mileage by approximately 0.5 mile per gallon. The actual fuel mileage improvement depends on the tractor-trailer aerodynamics, ambient temperature, gross weight, and tire type. As speed increases, tractors with poor aerodynamics will experience greater fuel economy loses than vehicles with better aerodynamics.
4. Tractor-Trailer Aerodynamics
The aerodynamic differences between two tractors close-coupled to a Dry Van can amount to 0.55 mpg or a 9% penalty.
The tractor-trailer gap for a high cube trailer (Dry Van, Reefer) is another factor affecting aerodynamics. A 6' gap can represent a 7.5% penalty or 0.45 mpg. Testing by a major OEM has shown that for every 10 inches of trailer gap, the fuel mileage changes 1%.
The tractor-trailer combination can represent up to 1.8 mpg or a 30% difference in fuel mileage penalty. This is based on a comparison between an aerodynamic tractor-trailer (Dry Van) with an 18" gap and a Car Hauler, both with 80,000 lbs Gross Combination Weight (GCW).
As you can see, the tractor-trailer aerodynamic package is another very large contributor to a vehicle fuel mileage performance. It is ironic that a tractor with poor aerodynamics can generate a larger trade-in residual value. A business decision should be made to weigh the additional fuel cost against the higher trade-in value of the tractor.
5. Climate Conditions and Weather
The average mid west winter months daily temperature of 25°F (-4°C) is responsible for a 13% fuel mileage penalty compared to summer time conditions of 70°F (21°C) or higher. Cold air is denser and increases the aerodynamic drag on the tractor-trailer. High winds, terrain, and snow-covered roads can also change fuel economy by an additional 13% compared to a calm day and well-maintained roads.
Winter fuel measuring 38 API gravity (lower energy/lower BTU content) is responsible for another 2.5% fuel mileage penalty.
The total AVERAGE MID WEST WINTER TIME (25°F/-4°C) penalty on fuel economy amounts to 15.5% (13% temperature + 2.5% winter fuel) or approximately 0.9 mpg. At 0°F (-19°C), the fuel penalty approaches 1.1 mpg.
Winter fuel with higher API gravity will generate a higher fuel mileage penalty. In the southern region of Canada, 41 API fuel translates into a 5% fuel mileage penalty (0.3 mpg). Further north, kerosene with 48 API gravity results in a 15% fuel mileage penalty (0.9 mpg).
7. Idle time
In terms of impact on fuel mileage, idling ranks near the bottom of the list of factors affecting fuel economy. This is not to say that idle time should be ignored. The cumulative effect of small improvements can be very significant. Idling, unless it is necessary to maintain a comfortable driver environment or provide PTO (power take-off) power, is unnecessary. With much less management time commitment and training effort, reducing vehicle speed by 2 mph (3% change) can improve fuel economy by nearly 0.2 mpg.
Tires are available with different types of tread design suitable for various applications.
Deep Lugs improve traction at the expense of higher rolling resistance. Shallow Lugs reduce the tread depth to decrease rolling resistance. Ribs sacrifice traction but offer lower rolling resistance and better fuel economy.
In addition, there are tall tires (11R24.5), low profile tires (285/75R24.5), and wide base / super single tires (445/50R22.5). The tall tires exhibit a little more rolling resistance because of the increased flex of the taller sidewall. Low profile tires have a weight advantage and less rolling resistance. The super single tires can provide up to an 800-pound advantage over duals on the tractor alone. A similar weight saving can be realized on the trailer. The super single tires offer the least rolling resistance. In actual application, one can expect an approximate 3 - 4% improvement in fuel economy with super singles installed on both the tractor and the trailer.
Some facts to consider:
- All tires are at their least fuel-efficient point when new. As the new tire wears, the rolling resistance decreases and fuel economy improves.
- The majority of the fuel economy advantage is obtained when the tread is 50% worn.
- Regular radial tires and fuel economy labeled tires provide nearly the same fuel economy as they approach wear out.
- Above 45 mph, air resistance/aerodynamics is a more important consideration than tire rolling resistance.
- Fuel-efficient tires loose half of their fuel efficiency benefit when vehicle speed increases from 60 to 75 mph.
- Retreads are nearly equal to new tires in rolling resistance.
The gearing of a tractor (drive axle ratio) is based on several factors including the drive tire revolutions per mile, transmission top gear ratio, engine torque rating, GCW, gradeability requirement, tractor-trailer aerodynamics, application, and vehicle speed. Gearing is a compromise between truck performance and fuel economy. Fuel cost is a substantial part of the total owning and operating cost (second to driver's wages) and therefore optimum gearing leans toward the fuel economy side of the equation.
Some operators of trucks geared for best fuel economy can compensate for any reduced performance by down shifting prematurely and more often to keep the engine rpm in the peak horsepower range. Driving in this manner defeats the purpose of "Gear Fast – Run Slow" and can lead to poor fuel economy and subsequent complaints.
10. Other Factors
There are several other variables that can affect fuel economy with on-highway applications. Road congestion, inadequate tire pressure, poor axle and front end alignment, vertical-rib and/or open-top trailers can have an adverse affect on fuel economy. Even small, seemingly inconsequential additions of bug deflectors or leaving the side windows open can also cost money.
Most fuel economy complaints can be explained with a basic understanding of some of the variables that affect fuel efficiency. These complaints typically occur during the winter months when fuel economy drops significantly. Customers purchasing new trucks during the winter months will experience this phenomenon. Not only do they suffer the fuel economy loses of the winter months but also have new tires and a minimum 30,000-mile "break-in" period to contend with. All new vehicle components (engine, transmission, drive axle, drive line U-joints, wheel bearings) require a "wear-in" period.