2008 Subaru Impreza Owner's Manual - Page 341

Maintenance and service 11-25 it off. . If the vehicle requires frequent refilling, there may be an oil leak. If you suspect a problem, have the vehicle checked at your SUBARU dealer. & Recommended grade and viscosity Each oil manufacturer has its own base oils and additives. Never use different brands together. Oil grade: API classification GL-5 WRX STI 1) Thermo switch 2) Drain hole 3) Oil level Remove the thermo switch from the filler hole and check the oil level. The oil level should be kept even with the bottom of the filler hole. If the oil level is below the bottom edge of the hole, add oil through the filler hole to raise the level. CAUTION . Be careful not to spill rear differential gear oil when adding it. If rear differential gear oil touches the exhaust pipe, it may cause a bad smell, smoke, and/or a fire. If rear differential gear oil gets on the exhaust pipe, be sure to wipe SAE viscosity No. and applicable temperature