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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.

CDL:

Commercial Driver's License (CDL)

A CDL is required to drive any of the following vehicles:

  • Any combination of vehicles with a gross combined weight rating (GCWR) of 26,001 or more pounds, providing the gross vehicle weight rating (GVWR) of the vehicle being towed is in excess of 10,000 pounds.
  • Any single vehicle with a GVWR of 26,001 or more pounds, or any such vehicle towing another not in excess of 10,000 pounds.
  • Any vehicle, regardless of size, designed to transport 16 or more persons, including the driver.
  • Any vehicle required by federal regulations to be placarded while transporting hazardous materials.

Review Questions - Click On The Picture To Begin...

What is the best way to determine what percentage of the weight of fuel will go to each set of axles?
  • The percentage is standardized amongst manufacturers and is the same for every truck
  • Simply go by the number of gallons of fuel each tank holds
  • Ask another driver what their numbers are
  • Weigh the truck immediately before and after fueling, and do a simple calculation

Quote From The CDL Manual:

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
Next
You weigh the truck immediately before and after fueling. Based on the following, determine what percentage of the weight goes to each set of axles:

Before fueling:
steer: 10,200, drives: 31,300, gross: 71,700
After fueling:
steer:11,000, drives: 31,500, gross: 72,700
  • 80% went on the steer axle
    20% went on the drive axles
  • 67% went on the steer axle
    33% went on the drive axles
  • 75% went on the steer axle
    25% went on the drive axles
  • 70% went on the steer axle
    30% went on the drive axles

Quote From The CDL Manual:

To determine the percentage of fuel weight added to the steer axle, take the weight added to the steer axle, divide it by the total fuel weight added (determined by the change in the gross weight), and then multiply that times 100

TruckingTruth's Advice:

To determine the percentage of fuel weight added to the steer axle, take the weight added to the steer axle (800 pounds), divide it by the total fuel weight added (1000 pounds), and then multiply that times 100

800/1000 = .8

.8 * 100 = 80% fuel weight to the steer tires

100% - 80% = 20% went on the drive axles.
Prev
Next
What is the safe number to use in calculations for the weight of fuel?
  • 8 pounds per gallon
  • 10 pounds per gallon
  • 6 pounds per gallon
  • 7.25 pounds per gallon

Quote From The CDL Manual:

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.
Prev
Next
Where will the weight of fuel be distributed?
  • Entirely on your drive axles
  • Mostly to your steer axle, with some going onto the drive axles.
  • Mostly to your drive axles, with some going onto the steer axle.
  • Entirely on your steer axle

Quote From The CDL Manual:

The weight of the fuel in your tanks will be distributed mostly to your steer axle, with some going onto the drive axles.
Prev
Next
You weigh the truck immediately before and after fueling. Based on the following, determine what percentage of the weight goes to each set of axles:

Before fueling:
steer: 11,450, drives: 33,100, gross: 76,700
After fueling:
steer:11,850, drives: 33,300, gross: 77,300
  • 67% went on the steer axle
    33% went on the drive axles
  • 88% went on the steer axle
    12% went on the drive axles
  • 75% went on the steer axle
    25% went on the drive axles
  • 73% went on the steer axle
    27% went on the drive axles

Quote From The CDL Manual:

To determine the percentage of fuel weight added to the steer axle, take the weight added to the steer axle, divide it by the total fuel weight added (determined by the change in the gross weight), and then multiply that times 100

TruckingTruth's Advice:

To determine the percentage of fuel weight added to the steer axle, take the weight added to the steer axle (400 pounds), divide it by the total fuel weight added (600 pounds), and then multiply that times 100

400/600 = .67

.67 * 100 = 67% fuel weight to the steer tires

100% - 67% = 33% went on the drive axles.
Prev
Next
You weigh the truck immediately before and after fueling. Based on the following, determine what percentage of the weight goes to each set of axles:

Before fueling:
steer: 11,100, drives: 32,600, gross: 71,400
After fueling:
steer:11,850, drives: 32,850, gross: 72,400
  • 80% went on the steer axle
    20% went on the drive axle
  • 65% went on the steer axle
    35% went on the drive axles
  • 75% went on the steer axle
    25% went on the drive axles
  • 67% went on the steer axle
    33% went on the drive axles

Quote From The CDL Manual:

To determine the percentage of fuel weight added to the steer axle, take the weight added to the steer axle, divide it by the total fuel weight added (determined by the change in the gross weight), and then multiply that times 100

TruckingTruth's Advice:

To determine the percentage of fuel weight added to the steer axle, take the weight added to the steer axle (750 pounds), divide it by the total fuel weight added (1000 pounds), and then multiply that times 100

750/1000 = .75

.75 * 100 = 75% fuel weight to the steer tires

100% - 75% = 25% went on the drive axles.
Prev
Next
What is the correct method of determining what percentage of fuel is distributed between the steer axle and the drive axles?
  • Weigh the truck after running 100 miles, then immediately fuel up, and then re-weigh the truck to see what percentage of the added weight went to the steer axle, and what percentage went to the drive axles.
  • Weigh the truck immediately after fueling, then run exactly 100 miles, and then re-weigh the truck to see what percentage of the added weight came off the steer axles.
  • Weigh the truck, then drive exactly 100 miles, and then re-weigh the truck to see what percentage of the added weight went to the steer axle, and what percentage went to the drive axles.
  • Weigh the truck, then immediately fuel up, and then immediately re-weigh the truck to see what percentage of the added weight went to the steer axle, and what percentage went to the drive axles.

Quote From The CDL Manual:

In order to accurately determine what percentage of fuel weight goes to your steer axle versus your drive axles you can simply weight the truck, then immediately fuel up, and then immediately re-weigh the truck to see what percentage of the added weight went to the steer axle, and what percentage went to the drive axles.
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