Towing, caravans and bike racks: how much more fuel

The short answer

• A caravan can more than double fuel use: in promobil’s test, at 100 km/h, it rose by 151–155%.
• Bikes on the roof or the tailgate raise fuel use by 23–44%; on a tow-bar rack, by 4–6%.
• When towing, speed matters most: in Spain the limit is 90 km/h (56 mph) on motorways and 80 km/h (50 mph) on single-carriageway roads.
• Take the bike rack and roof bars off as soon as you’re done with them: empty roof bars cost fuel too.

Bike racks: tow bar beats roof

ÖAMTC and ADAC tested three types of bike rack with two e-bikes in 2022. On the roof, the bikes stand upright in the full airflow, and on the tailgate they sit crosswise. On the tow bar they sit lower and behind the car, and cost much less.

ADAC, in the same test, reports almost identical figures at 130 km/h: 6.3% more on the tow bar, 34.2% on the roof and 44.3% on the tailgate. The catch with a tow-bar rack is that you need a tow bar. If you carry a roof box, see roof boxes and luggage: the effect is similar.

Caravans: aerodynamics matter more than weight

German magazine promobil tested a Skoda Karoq 2.0 TDI 4x4 towing two caravans in 2026: a small one at 1,000 kg and a large one at 1,600 kg. Without a caravan, the car used 5.1 L/100 km at 100 km/h.

Two things stand out. First, the large caravan, 600 kg heavier, used slightly less than the small one, because its shape was more aerodynamic. Second, driving at 80 instead of 100 km/h saved 20%. With a caravan behind you, air resistance soars with speed, just as with a car on its own but with far more surface: see fuel consumption by motorway speed.

Enclosed and cargo trailers

Oak Ridge National Laboratory (ORNL, US) tested an SUV towing an enclosed trailer of about 1,588 kg (3,500 lb): fuel use rose by 30% on the city cycle and by up to 50% at 129 km/h (80 mph). At that speed, the engine was so heavily loaded that it ran a richer mixture to protect itself, which pushes fuel use up even further. A low, open trailer has less drag than a tall enclosed one, but its weight still counts when accelerating and climbing.

Tips

• For bikes, a tow-bar rack beats a roof or tailgate rack.
• With a caravan or trailer, drive at 80–90 km/h (50–56 mph). It’s the legal limit on Spanish motorways, and in promobil’s test, 80 instead of 100 km/h saved 20%.
• If you’re buying a caravan, look at the shape of its front, not just its weight.
• Raise the car’s tyre pressures to the full-load figure the manufacturer gives, and check the caravan or trailer tyres too: tyre pressure and fuel consumption.
• Take the bike rack and roof bars off when you get back.
• The calculator doesn’t model trailers or caravans. To estimate a trip, enter as “My real figure” what you measured on a previous trip with the same combination, or start from the data in this guide. With bikes on the roof, the “Roof rack or box” option falls short: calculator. If you travel by campervan or motorhome, see campervan and motorhome fuel consumption.

Frequently asked questions