Diesel consumption for heavy trucks: does it vary depending on the load and the road?

Heavy trucks are the backbone of the world's transportation sector. They transport goods and raw materials between cities and countries over long distances. However, its high consumption of diesel makes fuel one of the biggest operating costs for carriers. According to the International Energy Agency (IEA), heavy trucks consume more than 40% of global road transport fuel.

Here the question arises: Does diesel consumption remain constant regardless of the load and the road? Or are there factors that make the truck consume more or less?

In this article, we will simplify the picture for you clearly and easily, and review the latest studies and statistics to understand the relationship between: fuel consumption, load, and road.

Why is it important for us to understand diesel consumption in trucks?

Before we get into the details of the impact of cargo and road, it's important to understand why fuel consumption in heavy trucks is a very important topic. It is not limited to financial costs only, but extends to the environment, profitability and even the sustainability of the transport sector.

A statistic from the U.S. Federal Highway Administration (FHWA) confirms that improving fuel efficiency by 10% in a fleet of 100 trucks can save more than $500,000 per year.

1. Operating cost:

Fuel typically accounts for 25% — 35% of the operating cost of carriers.

2. Environmental impact:

More fuel consumption means more CO2 emissions, which increases corporate responsibility towards the environment.

3. Profitability:

Improving fuel consumption by a small percentage (5— 10%) may save fleet companies millions of riyals.

As a practical example, one of the transport companies in Europe, which operates a fleet of 250 trucks, stated in its annual report 2023 that it was able to reduce diesel consumption by 9% after training drivers in economical driving, saving the company nearly 1.2 million euros in one year.

A Gulf case study: a Saudi road transport company showed that its commitment to regular maintenance programs and balanced load distribution contributed to reducing consumption by 7%, which is equivalent to about 3,000 liters of diesel per month per truck.

The effect of load on diesel consumption

As the load increases, the more effort is required from the engine and, consequently, diesel consumption increases.

1. Overweight = increased consumption:

Transportation Research published a study in 2024 that showed that a 10% weight gain may raise fuel consumption by up to 5— 8%.

2. Illegal overloads:

It leads to a much greater increase in consumption, as well as the risk of tire damage and overturning.

3. Empty pregnancy:

Even when traveling without a load, the truck still consumes high fuel due to its self-weight and air size.

Application example:

A truck consumes 35 liters per 100 km with a regular load. Its consumption may reach 38 l/100 km when overloaded by 15%.

The effect of the road on fuel consumption:

Fuel consumption in trucks is not limited to the cargo only. The road on which they travel also plays a pivotal role. Driving on a mountain road is radically different from driving on a paved highway, and weather conditions may increase fuel consumption significantly. It is therefore essential to understand how diesel efficiency changes depending on the type of road and the surrounding conditions.

1. Mountain roads and slopes:

Walking downhill by 6% increases consumption by 9-12% compared to a flat road.

In a report issued by the U.S. Department of Transportation (USDOT), it confirms that fuel consumption increases significantly on high roads due to the force of gravity acting.

2. Off road vs off road:

Dirt or gravel roads increase fuel consumption by 15— 20% due to loss of grip and higher resistance. In a study by NHTSA, it indicated that traveling long distances on unpaved roads reduces fuel efficiency and increases tire failure.

3. The effect of weather and road conditions:

Walking in the rain increases consumption by 10-15% due to water resistance. Snow and ice have doubled consumption in some cases.

A realistic comparison between different models:

In the United States, heavy trucks consume about 39 billion gallons of diesel per year (out of 54 billion gallons of fuel for trucks), according to a report published by Trucking Industry in the United States).

• Engine technical condition:

Engines that are old or have not been periodically repaired consume 7— 9% more fuel.

• Weight and road together:

In a study from Oak Ridge National Laboratory (2022), it was shown that the impact of the load becomes greater on mountain roads compared to flat roads.

How can fuel consumption be reduced?

Some may think that fuel consumption is a constant and uncontrollable thing, but the reality is quite different. According to the U.S. Environmental Protection Agency (EPA), diesel consumption can be reduced by up to 15% by improving driving style only, without any technical changes. This means that there are practical and simple solutions that can directly reflect on corporate profits and reduce environmental impact.

1. Driver behavior:

Quiet driving reduces consumption by up to 12— 15%. Avoiding sudden acceleration and frequent stops also helps achieve this goal.

2. Truck maintenance:

Changing the air and diesel filters periodically, and making sure to calibrate the tire pressure, these points help to ensure a reduction in fuel consumption.

Don't forget that lower tire pressure = higher consumption

3. The use of modern technologies:

Platooning Convoy System:

It reduces air resistance and saves up to 10% of fuel.

Smart fleet management systems:

They help monitor consumption and identify the most efficient drivers.

The role of smart cargo and planning

Payload is not just weights added to a truck. It is a key factor in determining the amount of fuel consumed on the road. The method of distributing it and pre-planning the itinerary can make a clear difference between high or low fuel consumption. Multiple studies have shown that smart load management contributes to reducing costs and improving transport efficiency. Therefore, you should follow the following:

• Balanced load distribution reduces consumption and prevents tire wear.
• Planning shorter and less crowded routes saves fuel and time.

In a European study published in 2020, this study found that improving logistics planning alone may reduce fuel consumption by 8%.

The future: diesel alternatives:

Before we review diesel alternatives, it is important to realize that seeking new fuel sources is no longer a luxury, but a necessity imposed by high costs and environmental emissions. The International Energy Agency reports that switching to cleaner alternatives can save billions of dollars a year and reduce emissions significantly.

• Natural gas (LNG):

It is used in some countries as an alternative that reduces diesel consumption and saves 20-25% in cost.

• Electric trucks:

Its sales rose by 175% in the first half of 2025 in China, leading to a significant drop in demand for diesel, according to a report published by Reuters.

• Hydrogen:

It is expected to be one of the main future replacements for heavy trucks for long distances.

In conclusion...

Diesel consumption in heavy trucks is not a fixed figure. It is directly affected by load, road type, weather conditions, and even driving style.

Although these factors may seem out of control at times, a proper understanding of them helps companies and drivers reduce consumption, reduce costs and increase safety.

While diesel remains the primary fuel today, the future has cheaper and more sustainable alternatives, but until then, the solution remains smart load management, continuous maintenance, and the adoption of modern technologies.

Conclusion... Every extra kilogram on a truck, and every kilometer on a bumpy road, has a cost in fuel consumption. Be aware... and save on diesel to save your pocket and your environment.