Winter car camping at -10°C can lead to hypothermia, experts warn. An experiment in a new hybrid vehicle (Toyota Crown Estate) showed that a single blanket is insufficient to stay warm until morning. Running the engine is not a safe heating solution.
For a comfortable sleep, a flat sleeping area, a power source for heating (e.g., from a hybrid battery), and proper lighting are critical. Without these conditions, sleeping in a car at -10°C with only one blanket is impossible.