Depending on your load weight, you might have to very carefully watch and calculate your fuel weight distribution because you are already so close to the legal weight limit. That means, when fueling, being careful how much fuel you add and looking forward to your next refueling stop to see how long (far) you can travel. The placement of the fuel tanks, and the weight of the fuel itself, together have an effect on fuel weight distribution and fuel management – particularly when the legal weight limit looms closer and closer due to fuller and fuller loads.
Fuel Weight
Depending on humidity and temperature, precise diesel fuel weights vary. Ordinarily, a general rule of thumb can be between 7.5 and 7.25 pounds per gallon. When you’re doing your calculations, the number you can safely plug-in would end up being approximately 8 pounds per gallon. At least, today, that’s the number we’ll use.
Onboard Fuel Weight Distribution
Though some of your fuel tank weight is distributed onto the drive axles, most will be distributed to your steer axle. Based on the placement of your tanks relative to your drive axles and steer axle, from truck to truck, the percentage of weight that goes to each set of axles varies. To figure out what fuel percentage will go to the axles, some simple calculation will be done involving weighing the truck right before fueling and immediately after fueling.
Determining Fuel Weight Distribution
Naturally, the determination of fuel weight distribution will involve weighing the truck. To make an accurate determination of fuel weight percentages to your drive axles and steer axle, you first must weigh the truck before fueling. After fueling, the truck should be re-weighed. You will now be able to see what percentage went to which axles. Some sample calculations can be found below.
Your scale ticket before fueling read as follows:
- Gross – 34,000
- Breakdown: trailer – 13,000, drives – 13,000, steer – 8000
Your truck, re-weighed after the addition of 100 gallons of fuel, would generate the following scale ticket:
- Gross – 34,800
- Breakdown: trailer – 13,000, drives – 13,100, steer – 8700
What do these scale tickets tell you? 800 total pounds of fuel was added to your gross weight. 100 pounds went to the drives, 700 pounds went to the steers. To determine the percentage of fuel weight going to the steer axle:
- Take the fuel weight added to the steer tires
- Divide it by the total fuel weight added
- Then multiply that by 100.
So, in this case, 12.5% went to the drive axles and 87.5% went to the steers. This calculation method ends up being a valuable tool to truckers.
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