2003 Subaru Impreza Owner's Manual - Page 298

Driving tips D If your vehicle has an automatic transmission, avoid using the accelerator pedal to stay stationary on an uphill slope instead of using the parking brake or foot brake. That may cause the transmission fluid to overheat. Also, if your vehicle is equipped with an automatic transmission, avoid driving with the gear selector lever in "D" when towing a heavy trailer to prevent fluid overheating. A lower gear should be used. B Parking on a grade Always block the wheels under both vehicle and trailer when parking. Apply the parking brake firmly. You should not park on a hill or slope. But if parking on a hill or slope cannot be avoided, you should take the following steps: 1. Apply the brakes and hold the pedal down. 2. Have someone place wheel blocks under both the vehicle and trailer wheels. 3. When the wheel blocks are in place, release the regular brakes slowly until the blocks absorb the load. 4. Apply the regular brakes and then apply the parking brake; slowly release the regular brakes. 5. Shift into 1st or reverse gear (manual transmission) or "P" (automatic transmission) and shut off the engine. 8-38