YOU SEE THEM on every street and highway. Big trucks have aerodynamic fairings and tails, wide single tires, and rounded shapes. Today, with fuel around $4 a gallon, miles per gallon is king. And it's not just important for over-the-road vehicles. It impacts us all. Just think of how rising fuel costs have affected your bottom line.
Concrete producers cannot do many things long-haul truckers do. Aerodynamics has little effect on trucks operating less than 50 mph for most of their duty cycle. But that doesn't prevent us from doing other things to cut fuel costs. Each by itself may not seem significant, but together, they can lower fuel costs up to 20 percent.
The energy consumed by your trucks comes from just one place: the fuel you burn in your engine. Anything that lessens that energy demand saves you fuel. For example, if a bearing seal for the mixer drum starts to go bad and allows contaminants to get into the bearings, it will put a drag on the bearing. More power will be needed to turn the barrel. The added power requirement results in more burned fuel in addition to increased maintenance.
For years, truckers used dual tires under their loads to increase carrying capacity. Off-road tires often had deep lug tread patterns and very hard tread rubber for traction and resistance to damage. The downside was that these tires need a great deal of energy to overcome their inherent stiffness.
Using two tires instead of one requires twice the energy to flex the side-walls. Major tire manufacturers now offer wide-base single tires engineered for vocational and on-off highway use. They can save 3 percent to 4 percent fuel use. Changing from deep lug to shallow lug tires can save another 2 percent.
Engine lubricants have been improved, especially synthetic oils made from polyalphaolefin base stocks. For years, 15W-40 was the standard viscosity for commercial diesel engines, but 10W-30 synthetic oils can stand up to the rigors of heavy-duty work cycles. Thinner oils cut internal engine drag and save about 1.5 percent in fuel.
Using synthetics in the gear box and drive axles can save another 1 percent. Amsoil, the pioneer in synthetic oils, offers a heavy-duty, full synthetic 5W-40. The company claims that in SAE/TMC tests conducted against conventional 15W-40, fuel savings totaled 8.2 percent. Running the engine fan consumes 50 to 60 horsepower.
Running waterless coolant and adjusting the fan-on temperature can save up to 3 percent fuel usage in over-the-road trucks. With stop-and-go operations and using power take-offs, that could be more or less for producers.
According to the Technology and Maintenance Council's Recommended Practice RP1114, Driver's Effect on Fuel Economy, “Driver performance can account for as much as a 35 percent difference in fuel economy performance.” Variables include horsepower demand, vehicle speed, and brake use. Horsepower demand is directly related to acceleration rates. The quicker a driver accelerates, the more fuel he burns.
Braking also affects fuel consumption. Every time the brakes are applied, kinetic energy is converted to heat. The heat in the brakes is then dissipated to the air from the brake drums. The heat or kinetic energy is created from the engine burning fuel. Dissipate the heat and you're wasting fuel.
Drivers who can look to the next traffic light and time their approach, coast to stop signs, and ease up near the top of a hill so they can use gravity on the downhill side rather than slowing with the brakes use the least amount of fuel. These techniques account for up to 35 percent difference between the best and worst drivers.
Not long ago, engines had relatively narrow power bands, sometimes as little as 14 percent of total available engine revolutions (from 1800 to 2100 rpm). Today, engines run much slower, with peak torque as low as 1000 to 1100 rpm and peak horsepower at 1800 rpm. Modern engines can be driven across 45 percent of the rpm range, so shifting can occur at lower engine speeds.