Subaru WRX-STI Owner's Manual page 444

11-6
Maintenance and service/Maintenance schedule
NOTE
1) When the vehicle is used under severe driving conditions mentioned in the following examples*, the engine oil and oil
filter should be changed more frequently.
2) When the vehicle is used under severe driving conditions mentioned in the following examples*, inspection should be
performed at every 15,000 km (9,000 miles) or 12 months whichever occurs first.
3) When the vehicle is used under following areas, change fluid every 15,000 km (9,000 miles) or 12 months whichever
occurs first.
(1) High humidity areas
(2) Mountainous areas
4) When the vehicle is used under severe driving conditions mentioned in the following examples*, the air cleaner element
and air filter should be replaced more frequently.
* Examples of severe driving conditions:
(1) Operating in extremely cold weather (items 1, 2 and 18 only)
(2) Repeated short trips (items 1, 2, 14 and 15 only)
(3) Driving in dusty roads (items 9, 14, 15 and 20 only)
(4) Driving in rough and/or muddy roads (items 14, 15 and 20 only)
(5) Driving in areas using road salt or other corrosive materials (items 7, 14, 15, 16 and 18 only)
(6) Living in coastal areas (items 7, 14, 15, 16 and 18 only)