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How Fuel Efficient Are Semi Trucks? (19 Questions Answered)

Semi trucks have improved immensely over the years through many innovative methods.

Redesigning the exterior to decrease friction and utilizing lighter materials such as aluminum 5th wheels. 

The goal is always to get the most mileage out of each gallon of fuel, which translates to thousands saved each year when done right. 

Here’s a Short Summary to how Fuel Efficient Semi Trucks are:

Semi trucks are fuel-efficient at hauling loads over the road. On average they get 6 – 8 miles per gallon while pulling a gross weight of up to 80,000 pounds. Electric-driven semi trucks have a fuel consumption of 2 kWh per mile and are 3.37 times more efficient than diesel-driven semi trucks.

What does being Fuel Efficient mean to Semi Trucks?

Semi trucks are one of the most infamous gas-consuming vehicles on the roads. No one would argue with you if you said that they consume and burn a great deal of fuel whenever they travel. 

However, to compare a semi truck’s fuel consumption to that of an average passenger car is spurious. Of course, the average mile per gallon for a semi truck is far higher than that of a smaller car. 

Small cars can get up to 25-30 miles per gallon. Meanwhile, a semi truck only gets 6-8 miles per gallon on average. But, semi trucks pull far more weight than the average small car. 

The meaning of fuel efficiency for a semi truck is similar to what it means in a small vehicle. Fuel efficient semi truck means it is a truck that utilizes fuel effectively and with the least amount of waste.

But, it also means being able to crest hills effectively and haul over 80,000 pounds worth of merchandise without burning fuel excessively.

It means being able to travel large stretches without access to gas stations without the fear of running out of fuel. There is a lot on the line for a semi truck. 

How Fuel Efficient are Semi Trucks?

Semi trucks are not the most efficient vehicles around, however, for the weight, they are fairly efficient. This has gradually been improved over the years as well which has saved drivers a lot of money since semi truck drivers drive nearly 40,000 miles every year. 

Efficiency has improved over the years thanks to a number of changes to the construction of the vehicle becoming more aerodynamic, improved engine efficiency, and the use of electric-powered vehicles. 

What is the Average MPG for a Semi Truck?

Semi trucks today average between 6-8 miles per gallon. This is an improvement from the 1970s when semi trucks were getting around 5 miles per gallon. 

This depends somewhat on what type of truck you have, the size of your load, and the terrain in which you’re driving. This means that if you go uphill your truck can get as little as 2 miles per gallon, and up to 23 miles per gallon going downhill. 

Additionally, some trucks are hybrids where they combine electric-powered vehicles and diesel-powered vehicles. Some are even going fully electric with the new Tesla semi trucks being released. 

What makes a Semi Truck Fuel Efficient?

A number of aspects are tied into the fuel efficiency of a semi truck. These factors include the build of the truck, the ways in which the tires are inflated, and the speed at which you are traveling. 

You need to ensure that your truck is operating at its optimal capacity in order to guarantee that your truck’s fuel is being utilized optimally. 

Making sure your semi truck’s tires are inflated properly, you are traveling at the appropriate speeds, among other things all play into the fuel efficiency of your truck. 

Does the Type of Engine influence the Fuel Efficiency of Semi Trucks?

The type of engine definitely influences the fuel efficiency of your semi truck.

The engine needs to be designed to function in combination with the design of your truck, and innovations in idle and cruise control.

The PACCAR M11 and M13 engines are the best examples of this necessary combination for the maximization of fuel economy.

These engines were specifically designed to be lightweight, yet sturdy. The weight of the engine is a huge factor contributing to wasted fuel, so this lighter-weight engine is a good innovation. 

PACCAR also implemented cruise and idle control. Driving at high speeds actually burns excessive fuel unnecessarily, and idling wastes much more fuel than in regular cars.

The engines are equipped with cooling and heating mechanisms that help prevent the need for idling in cold weather. 

These features may seem small, but when combined they can save the driver a great deal of money.

The idling feature alone has helped drivers save $6-$8,000 a year in fuel. You can read more about this engine here.

Does the type of Fuel influence the Fuel Efficiency of Semi Trucks?

The most common fuel for semi trucks is diesel. Diesel is a petroleum-based fuel, like gasoline, however the way in which the engine burns it is different. Diesel is burned slower and by warming it up rather than sparking it with an ignition which maximizes its efficiency. 

Gasoline is occasionally used by semi trucks, but the engines of semi trucks are not designed for this fuel. Gasoline burns differently and it only produces some 125,000 BTUs of energy while diesel gets around 147,000 BTUs of energy. 

There are alternatives being explored and implemented for semi trucks, such as compressed gas and hydrogen. However, most semi truck drivers, for now at least, prefer diesel fuel.

Do Tires Influence the Fuel Efficiency of Semi Trucks?

Tires definitely influence the consumption of fuel in your semi truck. Good tires are one of the main contributors to wasted fuel on the road. 

Semi trucks maximize fuel by limiting the resistance they experience on the road, and well-inflated and designed tires are the main factors behind this.

If your tires are inflated poorly or have other wear weighing them down, you will want to get this corrected ASAP. 

It has been estimated that bad tires can increase your fuel consumption by 2%. This may not sound significant until you realize this translates to up to $10,000 annually on preventable waste. 

Does Pulling a Trailer with or Without Load influence the Fuel Efficiency of Semi Trucks?

Yes, the load you haul or do not haul has a large influence on the fuel economy of your truck. It’s estimated that for every extra 1,000 pounds you take on in a load it decreases fuel economy by .5 percent. 

This is why it is important to minimize the weight of your overall truck as much as possible. This is why lighter engines and fifth wheels have been manufactured and added to newer models. 

The less your truck weighs outright, the more you can haul without wasting fuel. 

Does Driving with a Fuel Tank half empty VS full influence the Fuel Efficiency of Semi Trucks?

The main factor to consider here is the weight of the fuel itself. So, yes if your tank is half empty the weight of your truck will be lessened and the fuel economy will be improved. 

However, the savings here are really minimal, close to maybe 1% saved in fuel economy. But, it comes with a cost. Driving near empty is risky since you can risk breaking down. 

Also, driving on an emptier tank can cause you to need to refuel at more expensive stations, and waste a lot of time waiting and idling. 

So, the cost really does not outweigh the benefits of fueling before you leave and going as far as you can before refueling at a preferred spot.  

Do Aerodynamics influence the Fuel Efficiency of Semi Trucks?

The build of your semi truck has a heavy influence on the fuel efficiency of your truck. Aerodynamic design has helped to limit the friction and resistance trucks face on the road and thus limit wasted fuel. 

The aerodynamic build has contributed to up to 14% in saved fuel over a year’s time. Peterbilt trucks for example tend to get to 10mpg, which is a good 4 gallons saved for miles.

Over a year’s time, this can translate to thousands of dollars saved on fuel. 

Does driving Uphill or Downhill influence the Fuel Efficiency of Semi Trucks?

Driving uphill can decrease your fuel economy to a measly 2mpg, especially when you are hauling a large load. 

Traveling downhill, however, will likely get you up to 20-23mpg.

The best way to help mediate this issue is to try to plot your routes prior to departure and try to avoid uphill climbs as much as possible. 

Does the way you Drive Influence the Fuel Efficiency of Semi Trucks?

Many estimate that the way a truck driver operates their vehicle has a strong influence on its fuel economy.

Maintaining a level speed of between 40-65mph is one of the best speeds for most semi trucks to keep. 

Cruise control is your best friend in this department. Trucks can save up to 6% of fuel by maintaining steady speeds and limiting stopping.

Accelerating your vehicle consumes more fuel than driving at a steady speed, so try to maintain your speeds and avoid roadways with a lot of stopping and going. 

What effect does City Driving VS Long Distance driving have on Fuel Efficiency?

City driving is far more fuel-intensive than long-distance driving primarily because of the consistent stopping required. 

Accelerating after stopping is one of the most fuel-intensive parts of driving a semi truck.

Your semi truck will get the most out of their fuel by consistent speeds on the highway where stopping is limited and acceleration is limited. 

Does Frequent Maintenance influence the Fuel Efficiency of Semi Trucks?

Yes, a well-maintained truck will get better fuel economy overall. Estimates are that a well-maintained semi truck can get up to 5-10% better fuel economy. 

The primary areas of focus for maximizing fuel economy include intake systems, exhaust systems, tire maintenance and alignment, and fuel filters. 

What is the most Fuel Efficient Semi Truck?

Kenworth T680 and Peterbilt 579 are two of the best semi trucks for fuel economy available.

They are some of the newest models from these brands and have PACCAR engines. On average they get around 10mpg, which amounts to significant savings. 

Another excellent model is the Freightliner Evolution, which has been greatly redesigned to maximize fuel efficiency through lighter parts and skillful exterior design. 

These models have come a long way to improving their fuel economy. This has been accomplished through intelligent use of aerodynamic design and decreasing the overall RPMs while in cruise control to help limit fuel consumption on the highway.

What are the least Fuel Efficient Semi Trucks?

Mainly, the most inefficient semi truck models are the International brand built before 2007.

These models had not yet adopted many of the EPA regulations and thus did not maximize many of the beneficial methods of saving fuel. 

All things considered, however, CAT brand vehicles have not successfully integrated these regulations at all, and certainly, get the least efficient rating overall. 

How can you Determine the Actual Fuel Efficiency of your Semi Truck?

Fuel efficiency is found by calculating how far you can go per gallon. This is best found by tracking how far you go on a full tank prior to getting to the halfway mark of your fuel tank. 

This is useful in determining if your truck is performing up to par as per the average mile per gallon for the model you drive.

Also, compare this average to the averages of other semi trucks traveling on similar routes. 

If your truck is performing below average, it may be time to perform some maintenance on your truck. 

How can you Improve the Fuel Efficiency of your Semi Truck?

The best way to improve your semi truck’s fuel economy is through the way you drive and performing your truck’s routine maintenance.

Avoid idling, speeding, and excessive acceleration, and stopping. 

Check the tires of your semi truck and ensure they are aligned properly and inflated well.

If you have the funds, perhaps consider replacing old, heavier parts, with lighter, newer models made of aluminum or other metals. 

What about Electric Semi Trucks, are they Fuel Efficient?

This is a matter of some debate in both the trucking industry and amongst environmentalists.

Electric semi trucks are generally preferred by those who wish to avoid noxious fumes in cities and towns. 

However, as far as the efficiency of the vehicle, they are generally more fuel-efficient than diesel semi trucks. However, there are many speed bumps they must still overcome.

These include their overall presence on the road still being limited, and therefore it can be difficult to find a charging station.

Charging a semi truck can also take a long time, and thus cut into your profits in the long run.

But, many hybrids have saved truck drivers thousands of dollars a year, and so one day the electric truck may very well come to outshine the diesel truck.