Honda used an all-plastic fuel tank for the Insight—probably to reduce weight. Not a bad idea for all cars, since many older fuel tanks develop rust that clogs the fuel system. The evaporative emissions system on the Insight is similar to most other cars. The EVAP system is designed to minimize the amount of fuel vapor escaping to the atmosphere. Fuel vapor is temporarily stored in a charcoal-filled canister until it can be purged from the canister. Vapor displaced when filling the gas tank is also stored in the canister until it can be used by the engine.