For BMW PHEV vehicles, the gasoline engine is primarily used as a backup when the electric battery is depleted. The duration that gasoline lasts in the vehicle can vary based on driving conditions and how often the gasoline engine is used. Generally, if the vehicle is mainly driven in electric mode, the gasoline can last for several months without issues, but it's recommended to keep the tank at least a quarter full to avoid fuel degradation.
If the vehicle will be stored for an extended period without using the gasoline engine, using a fuel stabilizer can help prevent the fuel from degrading and ensure optimal performance when you do need to use it.
