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Heat is more than a comfort issue

Fuel cans in summer heat

A parked car can heat far beyond the outside air temperature. That is a good reason not to use the boot as a permanent fuel store and to follow the container manufacturer’s storage guidance.

Reading time: 7 minutes
Summer rule: carry a filled can only as long as needed, keep it out of direct sun and move it to a suitable lawful storage location after the journey.

Cars can become much hotter than the air

In an ADAC sun-exposure test, interior temperatures rose to nearly 60 °C even though outside temperatures remained below 30 °C. Everything stored inside the vehicle is exposed to that heat load.

A travel reserve is not permanent storage

A can needed for a particular trip is different from keeping fuel in the boot for weeks. Once the trip is over, storage rules for the actual location take over.

Avoid direct sunlight

ADAC Skipper also advises recreational boat users to keep fuel and spare cans away from heat and direct sunlight. The same planning principle is sensible for road travel: shaded, restrained and carried only when needed.

Check the can before a hot-weather trip

  • No cracks or deformation.
  • Cap and seal are intact.
  • The can is upright and firmly restrained.
  • No direct sun on the container where avoidable.
  • A suitable storage plan exists for after the journey.
Fuel smell is a warning: if fuel odour is noticeable outside the closed can, do not simply continue the journey. Move to a safe setting, keep ignition sources away and inspect the container and closure.

Frequently asked questions

Should a fuel can stay in the boot all summer?

Avoid unnecessary long-term storage in a hot vehicle. When the trip is over, use a suitable and legally permitted storage location.

How hot can a parked car become?

ADAC measured interior temperatures close to 60 °C in a sun-exposed vehicle while outside temperatures remained below 30 °C.

Should a can be opened to release pressure?

During transport the closure should be used as the manufacturer specifies. Do not improvise vents or open the can inside the vehicle.

Sources for this guide

The following authorities and documents were used for this guide. Where rules change, the current original source takes precedence.

  1. ADAC measurements of heat build-up inside parked cars [German]ADACMeasurements showing strong heat build-up inside parked vehicles in sunshine
  2. Fuel in a spare can: what is permitted? [German]ADACGerman transport quantities, container marking, restraint in vehicles, international travel and ferries
  3. ADAC Skipper safety guidance for fuel cans on recreational boats [German]ADAC SkipperKeeping fuel and spare cans away from heat and direct sunlight on recreational boats