Calculating gas mileage while towing a trailer
How to calculate towing mpg from a fuel-up, real percentage drops by trailer weight, and the changes that actually move the needle on fuel use.
Pulling a 5,000-pound travel trailer typically cuts a half-ton truck’s mpg by 30% to 50%. A 2024 Ford F-150 EcoBoost that gets 22 mpg empty often returns 11 to 13 mpg while towing. A 2024 Ram 1500 V8 drops from 19 to 10 or 11. There isn’t a clean formula because aerodynamics, terrain, and headwind matter as much as weight, but you can calculate your real number in two tank fills.
The two-tank method
This is the only way to get accurate towing mpg for your specific truck and trailer.
- Hook up the trailer with the load you’ll be carrying.
- Fill the tow vehicle to a full tank. Click the pump off, click off again. Don’t top up past auto-stop.
- Zero the trip odometer.
- Drive at least 100 miles. More is better.
- Fill up again at the same pump style (auto-stop again). Record gallons added.
- mpg = miles driven divided by gallons added.
Example: 247 miles driven, 22.3 gallons added. 247 / 22.3 = 11.1 mpg. That number is real and beats any rule of thumb.
Tow about the same load on similar roads when you measure, or the result will be misleading. Mixed city and highway gives a working average. Pure highway gives the best-case number.
What the percentage drops actually look like
The 10/15/25/35 rule that gets repeated online is roughly right but oversimplifies. Real-world drops from a few tests across truck owner forums and Hagerty/Edmunds towing tests:
| Trailer weight | Type | Typical mpg drop |
|---|---|---|
| Under 2,000 lb | Open utility, small boat | 10% to 20% |
| 2,000 to 4,000 lb | Small camper, car hauler with compact car | 20% to 30% |
| 4,000 to 6,000 lb | Mid-size travel trailer, full car | 30% to 45% |
| 6,000 to 9,000 lb | Larger travel trailer, enclosed cargo | 40% to 55% |
| 9,000+ lb | Fifth wheel, heavy equipment | 50% to 65% |
Aerodynamics is doing most of the work. A 4,000-pound flat-faced travel trailer hurts mpg more than a 6,000-pound car on a low car hauler. A 30-foot trailer at 70 mph has roughly twice the drag of the same trailer at 55 mph. That’s where slowing down pays off.
What actually changes mpg
Speed. Drop from 70 to 60 mph and most tow rigs gain 1 to 3 mpg. Drop to 55 and add another 1 to 2 mpg. Diesel trucks see the smallest gains; gas trucks with smaller engines see the biggest.
Headwind. A 20 mph headwind into a tall travel trailer can cost 2 to 4 mpg by itself. Some days the math just doesn’t work.
Terrain. Long grades hammer fuel economy. The Rockies, Smokies and Sierras are mpg killers. Flatland states (Kansas, Florida, eastern Texas) read better.
Tire pressure. Underinflated trailer tires cost 1 to 2 mpg easily. Run them at the sidewall max (usually 50 to 65 psi for ST tires, 80 psi for LT tires). Truck tires: follow the door jamb sticker for the loaded condition.
Weight distribution. A trailer with tongue weight at 12 to 15% of trailer weight tracks straight at speed. A trailer too light at the tongue fishtails. A trailer too heavy at the tongue squats the truck and adds drag.
Engine choice. Heavy-duty diesels (6.7L Cummins, 6.7L Power Stroke, 6.6L Duramax) tow heavy loads at 9 to 13 mpg. Gas half-tons typically run 8 to 11 mpg with similar loads. Diesel pays back the upfront cost only at high mileage and heavy use.
Things that don’t help much
Wind deflectors. A roof-mounted deflector saves maybe 0.5 mpg on a half-ton with a tall trailer. Real number, not the “3 to 5 mpg” some sellers claim.
Fuel additives. Most don’t change mpg measurably. A few help with carbon buildup over time but won’t show up tank to tank.
Premium fuel on an engine that doesn’t require it. The owner’s manual tells you what fuel the engine actually needs. Putting 93 octane in an engine spec’d for 87 octane is a waste of money.
Quick math for trip planning
To estimate towing mpg before a fuel-up:
- Look up your truck’s EPA highway mpg empty.
- Pick the percentage range for your trailer weight from the table above.
- Multiply.
Example: 2023 Chevy Silverado 1500 5.3L gets 22 mpg highway empty. Towing a 6,500-lb travel trailer (40% drop): 22 x 0.6 = 13.2 mpg.
Then plan fuel stops at 60% to 70% of your truck’s actual fuel range, not its empty range. A 26-gallon tank at 13 mpg gives ~340 miles, but range anxiety with a trailer is real. Stop every 200 to 250 miles.
What gets the best towing mpg
In 2026, the half-ton with the best real-world towing mpg is typically the Ford F-150 PowerBoost hybrid (10 to 14 mpg towing a mid-size travel trailer) and the GMC Sierra Duramax 3.0L diesel (12 to 16 mpg towing similar). Both beat gas V8 alternatives. The 2.7L EcoBoost F-150 punches above its weight too, especially with a smaller trailer.
EVs for towing (F-150 Lightning, Silverado EV, Rivian R1T) are honest at the math but their range halves under load. A 320-mile R1T tows about 150 to 180 miles before needing a charge.
FAQs
Does premium fuel help when towing? Only if your engine requires premium. Otherwise no measurable benefit.
Is diesel always better for towing? Better for heavy and frequent towing. For occasional 5,000-lb towing a few times a year, the diesel premium ($8,000 to $12,000 on a half-ton) doesn’t pay back.
Should I increase tire pressure when towing? Truck tires: yes, to the upper end of the door jamb sticker range for the loaded condition. Trailer tires: keep them at the sidewall max when loaded.