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Compensating For The Effects Of Fuel

There will be plenty of times where you're loaded close enough to the legal weight limits that you'll have to watch how much fuel you're carrying. You'll also have to watch how much fuel you put in when you're fuelling, and calculate when it will be ok for you to fuel up the next time. The weight of the fuel itself and the placement of the fuel tanks will both have an effect on fuel management and weight distribution while hauling loads close to the legal limit.

The Weight Of Fuel

The precise weight of diesel fuel will vary based on temperature and humidity, but is generally around 7.25-7.5 pounds per gallon. So the safest bet is to use 8 pounds per gallon as the number you'll plug into your calculations, and that's what we're going to use here.

The Weight Distribution Of Onboard Fuel

The weight of the fuel in your tanks will be distributed mostly to your steer axle, with some going onto the drive axles. The percentage of weight that goes to each set of axles will vary from truck to truck based upon the placement of your tanks relative to your steer and drive axles.

The best way to determine what percentage of your fuel will go to each set of axles is to weigh the truck immediately before and after fueling, and do a simple calculation.

Weighing The Truck To Determine Fuel Weight Distribution

In order to accurately determine what percentage of fuel weight goes to your steer axle versus your drive axles you can simply weigh the truck, then immediately fuel up, and then immediately reweigh the truck again to see what percentage of the added weight went to the steer axle, and what percentage went to the drive axles. Here's an example of how to do the calculations:

You scale your truck before fueling and receive your scale ticket. Here's the weights:

• Steer:
  8,000
• Drives:
  13,000
• Trailer:
  13,000
• Gross:
  34,000

After adding 100 gallons of fuel, you reweigh the truck immediately and here's your new scale ticket:

• Steer:
  8,700
• Drives:
  13,100
• Trailer:
  13,000
• Gross:
  34,800

So from looking at your scale ticket you can see from the gross weight that you've added 800 total pounds of fuel. 700 pounds went on the steers, and 100 pounds went on the drives. So to calculate the percentage of fuel weight to the steers versus the drives the forumula is:

Take the weight added to the steer tires (700 pounds) and divide it by the total fuel weight added (800 pounds) and then multiply that times 100:

700/800 * 100 = 87.5% went to the steer tires, and 12.5% went to the drive axles (100% - 87.5% = 12.5%). Now anytime you get fuel you'll know exactly where the weight will go.