Three Key Metrics of Fuel Efficiency
Since the early days of the automobile, motorists have been familiar with a single way of describing fuel efficiency. It’s represented by three very familiar letters: M, P, and G.
Miles per gallon is a reasonably effective means of measuring fuel consumption in light passenger cars. Cars have infinitely varied duty cycles, a common purpose (personal transportation), and no need to calculate the per-pound cost of moving cargo. This makes the simplicity of MPG appealing in the auto market.
Compare that relative simplicity to the world of fleet management, where a vast selection of truck designs, load weight and densities, terrains, and purposes make MPG not entirely irrelevant, but a rather weak way of establishing true efficiency. After all—in the world of trucking—each gallon of fuel is supposed to produce revenue. High MPG numbers mean nothing if they don’t pay the bills.
In these new days of fleet tracking platforms with features intended to increase fuel efficiency, it’s important to consider what they should be measuring. Three metrics are especially helpful to making fleets more profitable. All of them should be collected and analyzed by your fleet tracking solution.
The all-time greatest efficiency killer: at zero MPH, all trucks get zero MPG. That one fact drives down city MPG averages in both cars and trucks, no matter their weight. That time spent waiting at stop lights drives down economy. Modern cars save fuel that would otherwise be wasted at idle using automatic stop-start systems. Trucks, so far, make do without.
The all-time greatest efficiency killer: at zero MPH, all trucks get zero MPG.
To get an idea of where your fuel spend is going, it helps to know the time each rig spends at idle. This should be expressed in both a total and percentage. A high percentage of time spent idling can point to opportunities for improved routing, scheduling, or driver training. Your fleet management solution should collect and allow you to track idle time as a total and percentage.
Time Spent in RPM Bands
For max efficiency, a driver needs to use the gears to their greatest advantage. That means keeping the kettle on the boil at the truck’s optimum RPM range. Drivers develop a sense of when to shift in advance of need. The goal is to keep the RPM’s within that narrow range where max engine efficiency results.
Thus, fleet management software should track the amount of time (total and percentage) in each RPM band. This metric helps identify the drivers who understand how to get the most out of each gallon of fuel. More time spent in the higher or lower RPM range can indicate a problem with the driver, the truck, the load, or even all three.
OTR trucks spend a lot of time in cruise mode—humming along in a single gear with RPM’s kept in a very tight range. As mentioned above, that’s where the greatest efficiency can be achieved.
A truck on a regular route across flat interstate should remain in cruise mode most of the time, allowing for traffic and the occasional grade. Any truck that can’t sustain cruise mode under such conditions might be overloaded, misconfigured, or just need maintenance. Route optimizations and driver training can also help extend cruise.
Working to increase your fleet’s performance against these metrics will reduce real fuel costs. Whereas a lightly-loaded truck driving at a low speed can return impressive MPG numbers, what you’re looking for is maximum profit squeezed out of each gallon of diesel.
With fuel as the single greatest cost in operating a fleet, tracking and improving efficiency is critical for profitability and competitiveness.
That’s where an advanced fleet tracking platform—and savvy data analysis—comes in handy. With fuel as the single greatest cost in operating a fleet, tracking and improving efficiency is critical for profitability and competitiveness.