How Many Gallons Does a Semi Truck Hold?

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Semi-truck, being among the bulkiest modes of transportation, after freight trains, one cannot expect to consume a few gallons of oil. Among heavy vehicles, Semi-trucks are the largest guzzlers of fuel.

And as it covers long distances, like that of freight trains, the gas/oil holding capacity has to be of mammoth size, too.

So, understanding ‘how many gallons does a semi truck hold?’ is inevitably important for both the owners and operators to estimate the cost per trip of a semi-truck for transporting goods.

But sadly, not many people know much about them. Generally, the holding capacity of a semi-truck is 300 gallons. But that’s not the only figure, and it depends a lot on different factors.

In this piece, we are going to demystify some of the complexities about the holding capacity of semi-trucks, and some unexplored questions that have never come to your mind.

How many gallons does a semi truck hold

How Many Gallons Does a Semi Truck Hold?

So, how many gallons in a semi truck? A standard semi-truck contains two fuel tanks with around 120 to 150-gallon capacity.

Combine both, and you will get an answer of approximately 300 gallons. And they are placed on each side of the tractor. Placing the tanks on each side gives balance to the semi-truck.

It is not just for the sake of general understanding that we dig into this question.

But every aspect of a semi-truck is somehow connected to the state regulations, and to help you be wary during your logistic operations when you need to refill it.

Understanding The Need to Know About The Gallons a Semi-Truck Hold

Understandably, one might be confused about the need to know the answer to such a question. But it is pretty beneficial for truck operators to know the exact gallon capacity of their semi-truck.

It is due to the transportation laws that might differ from one place to another.

Without knowing the accurate tank capacity and the fuel weight, the semi-truck operator would be at risk of getting on the foul side of the law and having to incur heavy fines for unlawful transportation of goods on US soil.

After knowing the tank capacity, you could factor in the weight and avoid the tickets you might receive due to simple negligence.

Something of note that might help you is that a gallon of diesel usually weighs around 7 pounds. It would certainly come in handy for you.

Factors That Affect The Fuel Capacity

We have already mentioned that a standard semi-truck usually has two fuel tanks with around 120 to 150 gallons of capacity.

However, that is only usually the case. Multiple factors can impact the loading capacity of fuel tanks.

1. Size of The Fuel Tank

Yes, the first thing to note here is the size of the tank. Not every fuel tank is designed similarly. No, there are different sizes of fuel tanks.

However, the industry standard is a tank with a fuel capacity, as already stated. Larger tanks are only used for long-distance travel.

2. Type of Semi-Truck

Another factor that influences the fuel capacity of the semi-truck is its type. It would not surprise anyone to find more than one type of semi-truck in the market.

And naturally, they have their unique type of fuel tank attached to them.

The more the load a semi-truck is designed to carry, the more the fuel capacity of the tanks in the vehicle would be.

After all, the more weight the semi-truck trailer carries, the more power it would need from the engine, hence more fuel use.

3. Aerodynamics

The aerodynamics of the semi-truck also affect the fuel capacity of the semi-truck significantly.

Simply put, the better a semi-truck is aerodynamically designed, the better the fuel economy of the model will be.

With an aerodynamically designed truck, there would be less wind resistance, which eases the movement of the semi-truck.

The combination of all this would result in the engine needing less fuel to cover a larger distance compared to other semi-truck models in the same category.

So, the more aerodynamically a truck is designed, the lower the fuel tank capacity would be needed.

How Much Fuel Does a Semi-Truck Use?

Another question related to the capacity of the semi-truck is the fuel consumed by the semi-truck during its operation.

The standard answer is around 0.8 gallons per hour, but that is true only for heavy-duty trucks.

But as you might not have guessed, the answer to this question, like every question regarding the semi-truck, is complicated. And also dependent on many factors. So, let’s see what these factors are.

1. The Model of The Semi-Truck And its Weighing Capacity

It is something that is already alluded to in the previous point, the heavier the load carried by the semi-truck trailer is, the more power the engine would need to produce to move the vehicle, hence needing to burn more fuel.

It directly impacts the fuel consumption rate. So, one should not be surprised that the mileage shown by the heavy load-carrying semi-trucks is significantly lower than the other models.

2. How The Semi-Truck is Driven?

It might come as a bit of a surprise to many, although it really should not, that how the operator drives the truck does play a massive part in the fuel consumed by the machinery.

In case the semi-truck is driven by an operator who likes to drive aggressively, make sudden stops, and operate at speed, then the fuel consumption would be significantly higher than that of someone who drives much more calmly.

The reason behind that is pretty simple. As a result of more aggressive driving, the engine will use more fuel to provide optimal performance. Similarly, sudden acceleration and breaking of the semi-truck also waste a lot of fuel.

3. How Old is The Semi-Truck is?

Fuel consumption increases with age, even for minuscule tasks. Such is the case with semi-trucks as well.

The older the truck you have in your operation, regardless of its condition, it would consume more fuel than a newer model for the same task.

Another reason why that is the case is because of the less efficient engines that older semi-trucks used to possess.

The technology utilized in constructing a semi-truck engine has changed dramatically, producing more efficient semi-truck engines.

It is also one of the reasons why it is the standard practice by many transportation companies to overhaul their fleet after 10 to 12 years to make sure they would not have to pay extra in operational costs, which can be avoided.

4. Temperature

The climatic condition of the region the semi-truck is operating in also affects fuel consumption.

The simple equation here is that the cooler the climate is, the more fuel the semi-truck would burn to maintain the optimal temperature.

On the other hand, in hotter climate conditions, one would find a massive decrease in the amount of fuel consumed by the semi-truck engine as there are fewer energy requirements to maintain optimal working levels.

5. Tire Pressure

While this might come as a surprise, it really should not. The tire pressure does indeed play a role in influencing the fuel consumed.

If the semi-truck is adequately inflated, the fuel consumption would be in the optimal range. If such is not the case, then higher rolling resistance is bound to make it harder for trucks to move.

The difference can be minuscule at best on a small scale, but if the semi-truck continues to operate, there can be a massive impact on the operational costs. So, the semi-truck fleet operator must ensure that their vehicles are properly inflated.

How Can One Increase Their Mileage On a Semi-Truck?

The mileage of the semi-truck might be a concern for many of the semi-truck fleet owners. But there are also ways one can improve the mpg of their semi-truck and reduce their operational costs.

1. Slowing Down The Speed of The Vehicle

Moving the semi-truck at a lower speed is already recommended due to safety reasons.

But doing so also has the added benefit of increasing the mpg of the semi-truck. The slower the speed of the semi-truck, the lower the fuel consumption would be; it is as simple as that.

2. Cruise Control

Another way you can reduce the fuel consumption of your semi-truck is by trying for cruise control rather than aggressive acceleration and breaking during transportation.

Not only would doing so damage the cargo loaded on the semi-truck trailer, but it also impacts fuel consumption.

Instead, if the semi-truck operator goes with a steady pace, then they can save up to 6% in their fuel consumption.

3. Find The Sweet ‘RPM’ Spot

RPM, or Revolutions per minute, is an engine speed measurement. The more the engine has to work to maintain the speed of the semi-truck, the higher the fuel consumption is.

One would need to find that sweet spot where they not only get a suitable speed but would not ask the engine to do more work, which would only increase fuel consumption.

4. Check The Tire Pressure

A habit that the semi-truck operator would like to make a part of their lives is to check on the tire pressure every morning. There is a huge difference between inflated and underinflated tires regarding the fuel consumed.

An adequately inflated tire would make sure that one is in for a comfortable and smooth ride. The inflated tire would save fuel and would protect the tire from damage on the road as well.

5. Reduce Idle Time

Engine idle time is part and parcel of every semi-truck, and there is not much one can do about it, especially regarding long-distance transportation.

During the night, it is common practice for drivers of the said vehicle to stay inside them and utilize the facilities present in the semi-truck.

Now, one can utilize alternatives such as APUs (Auxiliary Power Units) or electrified parking spaces.

It allows them to use AC, TV, or any other electrical item without worrying about the impact on the semi-truck engine. The result in lack of idle time would only save the fuel burning.

The 95% Rule

The driver, according to this rule, is advised to only fill up the tank of their semi-truck to 95%. There are a couple of reasons for applying this method.

First, it avoids the risk of spillage. Second, the temperature of your driving environment influences the expansion and contraction of diesel fuel. One is also advised never to let the tank go below 25%.


Semi-trucks are among the most valuable pieces of equipment that a transportation company in the US could own. They are versatile and can cover long distances without any issues.

The answer to the question of how many gallons of semi-truck poses might not be straightforward, but no one can say it is not helpful.

However, now not only do you know the answer, but even the ways you can reduce fuel consumption.

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