Incorrect axle ratio inflates fleet fuel costs

Commercial fleet operators could cut their fuel bill by up to 3% by specifying the correct axle ratio when ordering new vehicles.

Research by Allison Transmission has revealed that making this simple change to a truck’s specification costs nothing – yet can bring a valuable reduction in running costs and carbon emissions.

Savings are likely to be greatest on duty cycles with frequent stop-starts around town or on minor rural roads.

Waste management company Biffa recently worked with Allison to determine optimal axle settings for Mercedes-Benz Econic refuse collection trucks with 270-, 300- and 350-horsepower engines. By running simulations on its iSCAAN software programme, Allison identified that switching these trucks from the standard 6.84:1 axle ratio to a shallower 6.0:1 ratio, also offered by Mercedes-Benz, could reduce fuel consumption by up to 3%, as well as lowering cab noise.

As a result, Biffa has amended its current order of 20 new Mercedes-Benz Econic trade waste collection vehicles, due to be delivered this autumn, with a further order of 18 to follow in spring 2023.

Simulations have shown that adopting axle ratios numerically lower than those offered as standard by OEMs can reduce fuel consumption by 1-3%.

Allison’s Continuous Power Technology has been developed to ensure there is no negative impact on the vehicle’s launch gradeability or productivity.

“Vehicle OEMs typically offer their fleet customers a choice of two or three factory-fit axle ratios and recommend one of these according to the country of use and application, making a sensible balance between performance and economy,” said Nathan Wilson, Allison’s UK account and market development manager.

“Historically, a deeper axle ratio setting has been the default selected by OEMs to provide the best gradeability for a 30 percent and above incline. While this delivers a good fit for many customers, in reality, gradients of this extreme are rarely encountered on UK roads. Meanwhile, the pressure to reduce costs and environmental impact has taken centre stage in recent years,” he added.