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Calculating The Amount Of Fuel You Can Take On

Ok, so you've loaded up at the shipper , you've scaled the truck at a truckstop, and you're getting ready to fuel up. Now you may not be able to just fill it up or you could be overweight at the next weigh station. But you want to put in as much fuel as possible so you don't have to stop more often than necessary. So how can you determine how much fuel you can add?

Remember that a safe estimate would be to figure each gallon of fuel weighs 8 pounds. Here's an example for calculating the amount of fuel you can take on based on the weight of the steer axle (we'll get to the drive axles in a bit):

You get loaded at the shipper and you scale your truck at a truckstop. Your steer tires are rated at 6,150 pounds, all of the states you're travelling in allow 20,000 pounds on the steer axle, and your fuel gauge is almost on empty. Here's your weights:

  • Steer:
    11,400
  • Drives:
    33,100
  • Trailer:
    33,700
  • Gross:
    78,200

Assuming that 90% of the weight of fuel goes to your steer axle and 10% to your drive axles, how much fuel can you put in and still remain legal on your axle weights?

Well, your steer tires are each rated at 6,150 pounds which means you can only be 12,300 on your steer axle. You're currently 11,400 on your steer axle so that gives you 900 pounds you can add to your steer axle. The formula to deterimine how much fuel you can take on based on steer axle weight is:

So for this example, here's how you would solve this step by step:

First, here's the numbers you know for the formula:
900 pounds (amount of weight available for steer axle)
90 percent (percentage of fuel weight to steer axle)

Step by step:

900/90 = 10
10 x 100 = 1000
1000/8 = 125 gallons of fuel you can add

Naturally, you have to be aware of the fuel weight that will be added to your drive axles so you have to make sure you won't wind up overweight on your drive axles either (34,000 pounds maximum). All you have to do to figure out how much weight will go on your drive axles is subtract the amount of weight going onto your steer axle from the total weight of fuel being added. In this case you're adding 125 gallons of fuel. You multiply the number of gallons times 8 to get the total weight of fuel being added:

125 x 8 = 1000 pounds of total fuel weight added

Then you subtract the amount going onto the steer axle from the total weight of fuel being added:

1000 - 900 = 100 pounds of weight going onto the drive axles

In this case we only started with 33,100 pounds on our drive axles so we'll be at 33,200 after adding 125 gallons of fuel

Calculating Fuel For The Drive Axles

Most of the time when you're worried about how much fuel you can add, it will be your steer axle that will be the limiting factor because most of the weight of fuel is placed on the steer axle. But sometimes the drive axles can be overloaded by adding fuel. The formula for calculating how much fuel you can add based on the drive axle weights is exactly the same as the steer axle weights except you plug in the amount of weight available to the drive axles and the percentage of fuel weight that goes to the drive axles:

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.

Shipper:

The customer who is shipping the freight. This is where the driver will pick up a load and then deliver it to the receiver or consignee.

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

Based on the following figures, how much fuel can you legally add while remaining legal on the steer axle?

Load rating of steer tires: 6,150 pounds
Percentage of fuel weight to steer axle: 85%
Steer axle weight limit in states you're travelling: 20,000 pounds
Weight Before Fueling: Steer: 11,500, drives: 33,100, gross: 76,700
  • 117.64 gallons of fuel
  • 110.75 gallons of fuel
  • 129.5 gallons of fuel
  • 133 gallons of fuel

Quote From The CDL Manual:

Once you know your current axle weights and the percentage of fuel weight that goes on the steer axle, you can use this formula you can calculate the amount of fuel you can take on:

TruckingTruth's Advice:

Because your steer tires are rated at 6,150 and the legal weight limit is 20,000 pounds for the steer axle in the states you're travelling in, the most restrictive law would be to not exceed the tire load rating. In this case, you can have 12,300 on your steer axle. Right now you have 11,500 on your steer axle, which means you can add 800 pounds to your steer axle and still be legal.

Because we know that 85% of the weight of fuel will go to the steer axle and you can add 850 pounds to your steer axle, we can plug the numbers into the formula above.

800/85 = 9.41
9.41 x 100 = 941
941/8 = 117.63 gallons of fuel you can add
Next
Based on the following figures, how much fuel can you legally add while remaining legal on the steer axle?

Load rating of steer tires: 6,150 pounds
Percentage of fuel weight to steer axle: 80%
Steer axle weight limit in states you're travelling: 20,000 pounds
Weight Before Fueling: Steer: 11,450, drives: 33,100, gross: 76,700
  • 119.5 gallons
  • 121.25 gallons
  • 146 gallons
  • 132.81 gallons

Quote From The CDL Manual:

Once you know your current axle weights and the percentage of fuel weight that goes on the steer axle, you can use this formula you can calculate the amount of fuel you can take on:

TruckingTruth's Advice:

Because your steer tires are rated at 6,150 and the legal weight limit is 20,000 pounds for the steer axle in the states you're travelling in, the most restrictive law would be to not exceed the tire load rating. In this case, you can have 12,300 on your steer axle. Right now you have 11,450 on your steer axle, which means you can add 850 pounds to your steer axle and still be legal.

Because we know that 80% of the weight of fuel will go to the steer axle and you can add 850 pounds to your steer axle, we can plug the numbers into the formula above.

850/80 = 10.62
10.62 x 100 = 1062
1062/8 = 132.75 gallons of fuel you can add
Prev
Next
Based on the following figures, how much fuel can you legally add while remaining legal on the drive axles?

Percentage of fuel weight to drive axles: 25%
Weight Before Fueling: Steer: 11,275, drives: 33,800, gross: 77,420
  • 100 gallons of fuel
  • 119.75 gallons of fuel
  • 122 gallons of fuel
  • 108.8 gallons of fuel

Quote From The CDL Manual:

Once you know your current axle weights and the percentage of fuel weight that goes on the drive axles, you can use this formula to calculate the amount of fuel you can take on:

TruckingTruth's Advice:

We know that 25% of the weight of fuel will go to the drive axles and you have 200 pounds you can add to the weight of the drive axles and remain legal. So plugging these numbers into the formula, you get:

200/25 = 8
8x100 = 800
800/8 = 100 gallons of fuel you can add
Prev
Next
Based on the following figures, how much fuel can you legally add while remaining legal on the drive axles?

Percentage of fuel weight to drive axles: 30%
Weight Before Fueling: Steer: 11,275, drives: 33,750, gross: 77,220
  • 110 gallons of fuel
  • 104.16 gallons of fuel
  • 112.75 gallons of fuel
  • 88.5 gallons of fuel

Quote From The CDL Manual:

Once you know your current axle weights and the percentage of fuel weight that goes on the drive axles, you can use this formula to calculate the amount of fuel you can take on:

TruckingTruth's Advice:

We know that 30% of the weight of fuel will go to the drive axles and you have 250 pounds you can add to the weight of the drive axles and remain legal. So plugging these numbers into the formula, you get:

250/30 = 8.33
8.33x100 = 833
833/8 = 104.13 gallons of fuel you can add
Prev
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