How Much Can Towing Affect MPG & Range? Here's What You Need To Know

According to the EPA, there are a number of reasons why your vehicle's mpg is going down. Those factors include things like high-speed driving, hilly terrain, and increases in cargo. It makes sense, right? Drive faster and there's more load on your engine, which requires more fuel — hence a reduction in fuel economy. These factors are all considered when rating a standard vehicle for fuel economy or range, but they all apply to towing a trailer too.

Adding a trailer to the mix means you're adding extra weight and drag. As a result, the load being moved by the tow vehicle's engine is greater, and fuel economy is reduced, no matter how small the trailer. The larger and heavier your trailer, however, the more effect it will have on your fuel economy or range. Some tests show range reductions in EV-powered pickup trucks as much as two thirds of overall range when towing a big trailer. Weight and size aren't the only factors, though. 

Factors like the shape of the trailer, the size of the vehicle pulling it, and the terrain you're trailering over all come into play too. With small, lightweight trailers, the reduction in range or the decrease in fuel economy can be relatively small, but with big trailers that get close to a vehicle's maximum towing limit, it can change things drastically.

In general, the larger a vehicle's towing capacity, the less effect the same-sized trailer will have on mpg and range. For example, towing a 1,000-pound trailer with a truck that maxes out at 2,000 pounds, will reduce fuel economy significantly. If you try to pull that same trailer with a truck like the F-150 that has a maximum towing capacity of 13,500 pounds, it represents a smaller percentage of the towing max so it won't be as big of a change. The closer you get to a vehicle's maximum towing capacity, the bigger effect it will have on fuel economy and range.

Every vehicle has some numbers associated with its weight. A vehicle's curb weight, for example, is how much it weighs when it leaves the factory with all the fluids in the engine and a full tank of fuel. Then, there's GCWR (Gross Combined Weight Rating) and towing capacity. GCWR is a measure of how much weight you can carry, including the vehicle's curb weight and the tongue weight of a trailer. 

The weight of a trailer that's distributed onto a vehicle's hitch is known as tongue weight. It's part of GCWR, and it can dramatically affect MPG. Poorly distributed weight on a trailer can increase or decrease tongue weight, which changes fuel economy even when towing the same amount of weight. So be sure to properly load your trailer if you want to optimize fuel efficiency while towing.

Both the shape of your trailer and the friction created by your trailer's surface can affect your fuel economy and range while towing. Even big trucks, designed with maximum towing capacity, deal with drag when they're moving. A big, boxy truck has more drag than a smooth, streamlined sports car, and the same principles apply to trailers. A square-shaped trailer will reduce your fuel economy more than a trailer that weighs the same amount, but has a lower drag coefficient due to a more aerodynamic design.

According to some truck-owner forums, mesh trailers are a particularly egregious offenders, dropping recorded fuel economy by as much as 6 to 7 mpg with minimal weight on the trailer. A likely culprit for the drop is the fact that mesh trailers aren't very smooth, so they trap air as they move along. On large tractor-trailer setups, these differences in fuel economy are even more pronounced, so you're likely to see all sorts of drag reduction devices fitted to modern trucks like wind skirts and cab spoilers designed to redirect air. 

The easier it is for air to move around your tow rig and your trailer, the better your towing fuel economy will be. Knowing exactly how much a trailer will reduce your specific vehicle's fuel economy or range is tough, but important factors like size, percentage of the vehicle's overall weight, and trailer drag will all come into play.