Diesel engines are preferred for long-distance hauling due to their superior fuel efficiency and torque. Diesel trucks can achieve 7-8 miles per gallon, compared to 4-6 mpg for gasoline trucks. With 40-50% more torque, diesel engines excel at hauling heavy loads, reducing fuel consumption, and improving durability—lasting up to 1 million miles before major repairs.

Fuel Efficiency

The popularity of diesel engines for long-distance trucking largely has to do with their exceptional fuel efficiency—a consideration that has been the key to the bottom line for the logistics industry. Diesel engines will generally see a 20-30% increase in fuel efficiency over their gasoline-powered cousins. For instance, a standard diesel truck can expect to see between 6.5 to 8 miles per gallon, while a similarly weighted gasoline engine might only reach 4-6 miles per gallon. This difference in fuel efficiency is directly translated into substantial savings on fuel costs, especially considering the longer-distance hauls that cover over 500 miles a day. Fuel is approximately 30-40% of a trucking company's operating costs, according to the American Transportation Research Institute, so even a small increase in fuel efficiency can translate into substantial cost savings in the long run. For example, if an organization operates a fleet of 100 trucks that run 500 miles a day, increasing gas efficiency by only a mile per gallon could save the organization $1.2 million in a year using average gasoline prices and use.

In addition to being gas-conscious, diesel engines are also extremely long-lived, indicating a lower cost of ownership over the lifetime of the vehicle. For example, diesel engines usually last 1.5 to 2 times longer than gasoline engines, with the lifespan reaching more than 1 million miles compared to a gasoline engine's 500,000 miles. This is due in part to the engine's sturdy design, which is built to withstand the increased compression ratios used in diesel engines. As a result, diesel engines require less maintenance and repair less frequently, and therefore represent lower total cost of ownership for long-haul fleets. The durability also affects fleet replacement cycles—diesel trucks will last longer before they must be replaced, potentially giving a better return on investment for trucking companies.

Maybe the most powerful aspect of diesel engines is their torque production, which is important in heavy-duty applications like long-hauling. Diesel engines produce 40-50% more torque than gasoline engines, and this makes them effective in carrying heavy loads, even uphill or on rough terrain. This is more so in the trucking industry, where trucks are often billed to haul commodities which weigh up to 80,000 pounds. The torque also enhances diesel engines to offer better performance when operating at low RPM, reducing fuel usage on long distances of driving. Such efficiency is one of the top reasons why haulers of long distances always turn to diesel engines as opposed to others. Research has shown that a typical diesel truck can travel at a 7% higher level of efficiency on extended, rising paths than gasoline trucks, ultimately conserving fuel over the long term.

A second reason diesel engines are utilized is due to the easy availability of diesel fuel across the United States. Unlike gasoline, which is potentially less accessible in remote areas or long stretches of rural roads, diesel fuel can be easily obtained in nearly any region of the country. Refueling a truck fleet during a cross-country run is facilitated by the fact that refueling sites are specifically designed to cater to the needs of diesel-powered trucks. The U.S. Energy Information Administration documents that there are over 60,000 diesel refueling facilities throughout the country. This large-scale infrastructure supports smooth operations for long-haul operators. Gas stations, however, are less frequently designed to support high capacities of fuel for big rigs, and this causes delays and additional costs for long-haul operators.

Also, the economic impacts of fuel efficiency can't be overlooked when considering the competitive landscape. Fuel costs can represent up to 25-35% of a trucking company's overall expenses. With volatile fuel costs, long-distance trucking fleets are constantly pressured to maximize fuel efficiency and keep operating expenses at a minimum. Diesel engines, with their greater fuel economy, give them an edge. In a recent report by the North American Council for Freight Efficiency (NACFE), it was discovered that fleets operating on diesel could save up to $30,000 per year in fuel expenses alone versus other engine configurations. This significant reduction in cost enables companies to improve their margins or pass the savings on to consumers, thus gaining competitiveness in a price-sensitive environment.

Engine Durability

Longevity is one of the strongest qualities diesel engines have that render them the most demanded for trucking over long distances. It is well known that diesel engines stand the test of time by surviving hard usage. Diesel trucks also last between 1.5 to 2 times longer compared to gasoline-powered trucks. Typically, a diesel engine can go up to 1 million miles, while a gasoline engine can go for some 500,000 miles before it requires extensive overhauling or replacement. This extended life means less maintenance and replacement expenses for trucking companies, and this is a big plus point in the long run.

As an example, a diesel engine replacement would require $10,000 to $25,000, depending on the make and model. But contrast the life of a diesel engine, 1 million miles versus 500,000 miles for a gasoline engine. Then the ROI is understandable. In the span of those million miles, a trucking company can save as much as $100,000 in engine replacement, based on fleet size and utilization. Diesel engines are thus more cost-effective in the long run, despite being more expensive upfront.

In addition, diesel engines are constructed to be capable of withstanding greater compression ratios than gasoline engines. Diesel engines operate on a compression ratio of 16:1 to 22:1, whereas gasoline engines operate on 8:1 to 12:1. The greater compression ratio gives the diesel engines more power and torque-yet harder. The engine parts are built to be sturdy enough to withstand these stresses, and that's why they all last so much longer under heavy loads. This is particularly applicable to haulage firms, where torque output is of the greatest importance. Diesel engines possess 40-50% more torque than gasoline engines and are thus best when transporting heavy loads. This extra power removes some pressure from the engine, resulting in its longevity.

Maintenance-wise, diesel engines are heavier-duty as they contain heavier, harder-wearing parts. For example, diesel engines contain heavier-duty pistons, cylinder heads, and crankshafts than gasoline engines, all of which are designed to be able to handle more heat and pressure. As it stands, diesel engines require less frequent overhaul and longer periods of maintenance—typically every 20,000 to 30,000 miles for major service inspections, compared to 10,000 to 15,000 miles for gas engines. This not only reduces downtime of operations for over-the-road truckers but decreases the overall cost of maintenance. A trucking company using diesel engine trucks can save 15-20% of its yearly maintenance expense compared to the use of gasoline-powered trucks.

Another reason for the long life of diesel engines is the way their fuel system is designed. Diesel engines are powered by a cleaner-burning fuel that lubricates the internal components so that they do not undergo premature wear and tear. Diesel fuel contains more energy density than gasoline, which enables the engine to operate longer without the need for refueling. Diesel engines also cruise at lower RPMs, which translates to less wear on components such as the engine bearings, pistons, and valves. This constant low-stress operation allows the engine to accumulate higher mileage without the loss of performance that is typical with gasoline engines.

Torque Advantage

One of the main reasons diesel engines are utilized for long-haul trucking is that they possess a torque advantage that is particularly useful when dealing with heavy loads in an efficient manner. Diesel engines possess significantly more torque than gasoline engines, with 40-50% more torque at lower RPMs. This is important for heavy trucks, which need constant power when transporting heavy loads over long distances. For instance, a typical diesel engine in a Class 8 truck will generate around 1,000 lb-ft of torque, while a gas engine will only generate 400-500 lb-ft under the same conditions. This capability allows diesel trucks to deliver more stable and efficient power, especially during acceleration or incline, with less fuel burn but still hauling the load with less engine strain.

In the aspect of towing capacity, the higher torque of diesel engines has a direct influence on the weight a vehicle can tow. For instance, a diesel truck is capable of towing 30% more than a gasoline truck. An average diesel truck can tow 20,000 pounds, while a gasoline truck can go up to 14,000 pounds. The additional torque also allows the diesel engine to keep the truck running at a constant speed even under challenging conditions, such as going uphill, off-road, or where the truck is loaded to capacity. This translates to fewer transmission shifts and overall smoother driving, particularly for long-distance driving with constant changes in elevation.

One of the benefits of diesel engines is that they can operate effectively at lower RPMs. Diesel engines operate at 1,200 to 1,800 RPM, and gasoline engines operate at 2,000 to 3,000 RPM. This lower RPM causes diesel engines to produce maximum torque when operating at cruising speed, so the engine does not have to exert itself as much to provide power. In fact, studies show that diesel engines are 20-30% more efficient at low to mid RPMs, which is a common scenario in long-haul trucking. Such efficiency means more mileage per gallon of fuel burned, which automatically equates to bottom-line savings for transportation and logistics firms.

Again, the high torque of diesel engines means more fuel economy when hauling heavy loads. For example, a heavy-duty diesel truck operating on the highway will cruise at 60-65 mph and will get around 7.5 to 8 miles per gallon of fuel. An equivalent payload gasoline engine will only get 5-6 miles per gallon under the same circumstances. The capacity to stay at higher speeds without more fuel offers a highly valuable competitive edge to trucking companies who have to sustain low fuel prices for the duration. When fuel cost is taken into consideration, as much as 30-40% of trucking company's operating cost is taken by fuel cost, then the torque advantage becomes all that much important.

The torque advantage applies to the engine's durability too. Diesel engines are built to handle the heavy torque they produce without experiencing unusual wear and tear. The stronger components of a diesel engine—such as hardened pistons and crankshafts—are made to withstand repetitive stresses of greater torque creation. In practice, the inner hardware of a diesel engine is typically 30% stronger than the inner hardware of a gas engine, which adds to the life of the engine. Diesel engines can typically last 1.5 to 2 times longer than gasoline engines before needing to be overhauled, with some of the diesel engines in big rigs exceeding 1 million miles before needing to be replaced or rebuilt.