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What will the fuel cost while towing?

Last updated Researched from published standards and manufacturer guides, not tested in person

Quick answer

The number that surprises people is the difference, not the total. Pulling a tall travel trailer commonly costs 30 to 50 percent of the tow vehicle unhitched fuel economy, because highway drag is dominated by frontal area rather than by weight once you are up to speed.

This is a consumer trip calculation. It is not cost per mile, it is not a business expense model, and it is not an owner-operator economics tool. Those are commercial trucking calculations and they live on our sister site rather than here.

What matters for a trip budget is the gap between towing and not towing, because that gap is the real cost of the trailer. Enter your own observed figures if you have them: a trip computer average over a previous towing trip beats any estimate.

Estimate the trip

From your own vehicle From your trip computer on a previous towing trip if you have it.
From your own vehicle

The trailer costs $150.46 extra on this trip, a 44.1% fuel economy penalty.

Your result
Figure Value
Gallons while towing 94.7
Cost while towing $341.05
Cost for the same trip unhitched $190.59
Extra cost of bringing the trailer $150.46
Towing penalty 44.1%

Shown with the example figures above. Change any field to run your own numbers.

The working

Published standard

gallons towing = miles / mpg towing cost towing = gallons towing x price per gallon the towing penalty = 1 - (mpg towing / mpg unhitched)

Plain arithmetic. The mpg figures are yours to observe rather than ours to supply. A published, traceable figure: a standards body, a federal regulation or a manufacturer specification states it.

The cheapest economy upgrade is correct tire pressure

Underinflated trailer tires add rolling resistance as well as heat, and heat is what destroys them. A gauge that reads past 60 psi and a monitor that watches while you drive are worth more than any fuel additive.

Every rating shown is the manufacturer's own published figure. The rating on the part you receive is what governs, and your own door jamb sticker governs everything above it.

Why weight matters less than you think

Once you are at highway speed on level ground, most of the fuel is going into pushing air out of the way, and aerodynamic drag scales with frontal area and with the square of speed. A tall slab sided travel trailer has an enormous frontal area and a shape nobody optimised, which is why the penalty is so large.

Weight dominates in two other places: climbing, where you are lifting the whole rig against gravity, and accelerating, where you are adding kinetic energy you then throw away at the next stop. On a flat interstate cruise it is mostly air.

The practical consequence: slowing down saves more fuel than lightening the load, on the flat. Dropping from 70 to 60 mph is a bigger change than almost anything you could take out of the trailer.

Typical towing penalties

These are observed ranges rather than published figures, and yours will differ. Use them only to sanity check a number you entered.

A tall travel trailer commonly costs 30 to 50 percent of unhitched fuel economy, and a low flat trailer much less.

Rule of thumb Widely taught towing convention rather than a published specification. It is a good starting point and it is not a rating.

What people commonly see
What you are pullingTypical penalty against unhitched
A low flat utility or boat trailer10 to 25 percent
A small or teardrop camper15 to 30 percent
A tall travel trailer30 to 50 percent
A large fifth wheel or toy hauler40 to 55 percent

Observed owner ranges, not manufacturer figures. Headwinds, grades and speed move them a long way, and a crosswind costs far more than a still day.

Cheap ways to reduce it

  • Slow down. The single biggest lever on the flat, and it also keeps you inside the speed rating of most ST trailer tires.
  • Correct tire pressure. Underinflated trailer tires add rolling resistance as well as heat, and heat is what destroys them.
  • Travel with empty fresh tanks where you can fill on arrival. Fifty gallons is 417 lb you are hauling over a mountain pass for no reason.
  • Tow in tow/haul mode. It changes shift points to keep the transmission out of a hunting cycle, which helps economy and helps the transmission far more.

Frequently asked questions

How much does towing hurt fuel economy?

Commonly 30 to 50 percent of the unhitched figure for a tall travel trailer, less for a low flat trailer and more for a large fifth wheel. The dominant factor at highway speed is frontal area rather than weight, because aerodynamic drag scales with area and with the square of speed. Your own trip computer average from a previous towing trip is far better than any estimate.

Does weight or aerodynamics matter more?

Aerodynamics, once you are at highway speed on level ground, because most of the fuel is going into pushing air out of the way. Weight dominates when climbing, where you are lifting the rig against gravity, and when accelerating. On a flat interstate cruise, slowing down saves more fuel than lightening the load.

Will slowing down actually save much?

Yes, more than almost anything else on the flat. Drag rises with the square of speed, so dropping from 70 to 60 mph is a large reduction in the work being done. It also keeps you inside the industry speed rating of most ST trailer tires, which is 65 mph unless the sidewall says otherwise, so it is a safety gain as well.

Does travelling with empty water tanks help?

It helps with climbing and acceleration rather than with flat cruising, and it helps a great deal with your cargo capacity and tongue weight. Water is 8.34 lb per gallon, so a 50 gallon tank is 417 lb. If you can fill at the campground, that is weight you are not hauling over a mountain pass for no reason.

Is this the same as cost per mile?

No. Cost per mile is a commercial owner-operator calculation that includes fixed costs, maintenance reserves, insurance, depreciation and the tax treatment of all of it. This is a consumer trip fuel estimate and nothing more. The commercial calculation lives on our sister site rather than here, because the two audiences need genuinely different tools.

Why is the difference more useful than the total?

Because the difference is the actual cost of bringing the trailer. The total includes fuel you would have burned driving there anyway, so it overstates what the trailer costs you and makes two trips of different lengths hard to compare. The penalty figure is what tells you whether a shorter route or a slower speed is worth it.

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Researched, not professional advice. This page is compiled from published standards, manufacturer towing guides and product specifications, and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are towing convention rather than published standards, and they are labelled that way wherever they appear. Nothing here overrides your own ratings. Work your payload sum before your tow rating, because payload is the limit that actually binds on most half ton trucks and nearly every SUV. Load a conventional trailer to 10 to 15 percent tongue weight and a fifth wheel to 15 to 25 percent pin weight, and never lighter: a tail heavy trailer is what starts sway. Weigh the rig loaded rather than trusting a brochure dry weight. A weight distribution hitch and a set of air bags both restore ride height and control, and neither one raises a single rating. Trailer brakes are required by state law above a threshold that varies by state, and a breakaway battery that has quietly gone flat is the normal condition of most trailers on the road.