From page 437 of the 2015 Forester owners manual: So if you have a manual transmission, you can tow 4 down.
Towing with all wheels on the ground
1. Release the parking brake and put the transmission in the N /neutral position.
2. The ignition switch should be in the ACC position while the vehicle is being towed.
WARNING . Never turn the ignition switch to the LOCK / OFF position while the vehicle is being towed be- cause the steering wheel and the direction of the wheels will be locked.
Remember that the brake booster and power steering do not function when the engine is not running. Because the engine is turned off, it will take greater effort to operate the brake pedal and steering wheel.
For CVT models, the traveling speed must be limited to less than 20 mph (30 km/h) and the traveling distance to less than 31 miles (50 km). For greater speeds and distances, transport your vehicle on a flat-bed truck