Modern, fuel-injected engines do not need to be warmed up, and unnecessary idling wastes fuel. If you anticipate being stopped for more than one minute, shut off the car. Restarting the car uses less fuel than letting it idle. If you’re driving a full hybrid, this is not an issue, because the gasoline engine automatically shuts down when the car is stopped, and the accessories – such as the air conditioning, lights, and stereo – operate off the juice stored in the battery pack. This is also one reason that hybrids often get better fuel economy in the city than on the highway – the gasoline engine is shut off when idling in traffic.