Complete Oil Specifications
Your 2021 Subaru Forester 2.5L requires 0W-20 full synthetic oil.
Quick Reference
| Specification | Value |
|---|---|
| Viscosity | 0W-20 |
| Standard | API SP / SN Plus |
| Capacity (with filter) | 4.4 quarts |
| Oil Filter | Subaru 15208AA15A |
| Normal Interval | 6000 miles or 6 months |
| Severe Interval | 3000 miles or 3 months |
Why 0W-20 is Critical for the Boxer Engine
The Subaru Boxer engine sits low in the chassis and relies on rapid oil circulation to reach horizontal pistons. 0W-20 oil flows instantly at startup to prevent dry wear on cylinder walls and camshafts. Subaru engines are also sensitive to oil level and quality. Low oil level can trigger the low oil light quickly.
Using thicker oil (like 10W-30) can cause:
- ❌ sluggish variable valve timing (AVCS)
- ❌ increased fuel consumption
- ❌ harder cold starts
Subaru-Approved Oil Brands
-
✅ Subaru 0W-20 Synthetic Motor Oil
-
✅ Idemitsu 0W-20 Advanced Moly
-
✅ Mobil 1 Advanced Fuel Economy 0W-20
-
✅ Castrol EDGE 0W-20
-
✅ Valvoline Advanced Full Synthetic 0W-20
Owners often recommend Idemitsu 0W-20 as it is the OEM supplier for Subaru oil.
Service Interval Check
Subaru recommends changing oil every 6000 miles or 6 months, whichever comes first.
Change closer to 3,000 miles / 3 months if you:
- Make repeated short trips
- Drive in extremely cold weather
- Tow a trailer
- Drive on rough/muddy roads (typical Forester adventure use)
Installation Details
Drain Plug Torque: 31 ft-lbs
Crucial: Always replace the crush washer (gasket) on the drain plug. Subaru crush washers are single-use.
OEM Filter: Subaru 15208AA15A
Aftermarket Filters:
-
WIX 57055
-
Fram XG7317
-
K&N HP-1010
Pro Tip: The oil filter is conveniently located on top of the engine bay. It has a high torque spec for a hand-tightened filter, so ensure it is seated firmly, but do not use a wrench to tighten it unless specified.
FAQs
What oil does a 2021 Subaru Forester take?
SAE 0W-20 synthetic motor oil.
How many quarts of oil does a Subaru Forester need?
4.4 quarts (4.2 liters).
Can I use 5W-20 or 5W-30?
5W-30 synthetic may be used for replenishment if 0W-20 is not available, but should be changed back to 0W-20 at the next oil change. 0W-20 is required for optimal fuel economy and cold start protection.
How often should I change the oil?
Every 6000 miles or 6 months. Do not extend intervals beyond this, as Boxer engines are sensitive to oil degradation.
Need these specs on your phone? Download OilFinderPro app for offline access and oil change reminders.
Last verified: 2026-02-23 | Source: https://techinfo.subaru.com/stis/doc/ownerManual/GSG/MSA5B2104A_STIS_2nd.pdf