The 2018 Subaru WRX features a 2.0-liter turbocharged direct-injection FA20F boxer engine that requires exactly 5.1 US quarts (4.8 liters) of engine oil when performing a standard oil and filter change. Getting the oil volume right on your WRX is critical because boxer engines sit low in the engine bay and rely on precise fluid dynamics for proper lubrication, cooling, and turbocharger longevity.
If you underfill or overfill your FA20F engine, you risk catastrophic oil starvation or excessive crankcase pressure that can blow seals. This guide breaks down the exact fluid requirements, viscosity choices, step-by-step change procedures, and troubleshooting tips for your 2018 performance sedan.
Factory Oil Capacity and Dipstick Realities
Subaru specifies two different oil capacity metrics in the owner's manual for the 2018 WRX:
- Total capacity: 5.5 quarts (5.2 liters) for a completely dry, factory-fresh engine build.
- Service fill (with filter): 5.1 quarts (4.8 liters) for standard maintenance oil changes.
One common frustration among owners is reading the factory dipstick accurately. The 2018 WRX dipstick features two holes (low and full). When you check your oil after a service fill, it's normal for the level to sit slightly below the top dot immediately after filling, or to fluctuate depending on whether the car has sat overnight versus being checked five minutes after shutdown.
Always check your oil on flat, level ground. Pull the dipstick, wipe it clean with a lint-free shop towel, reinsert it fully, and pull it out again. Aim to keep the oil level right at the upper dot. Running even half a quart low during aggressive cornering or highway pulls can cause oil pressure drops that damage the rod bearings.
Recommended Oil Viscosity and Specifications
For the 2018 WRX, Subaru officially recommends 5W-30 synthetic oil that meets API certification standards and bears the Resource Conserving mark.
While older naturally aspirated Subarus ran on 0W-20 or 5W-30 conventional oils, the turbocharged FA20F engine runs hot and places intense thermal stress on its oil supply.
- Standard Viscosity: 5W-30 is ideal for daily driving across all normal ambient temperature ranges.
- High-Performance or Track Use: If you track your WRX or live in extreme desert heat, many experienced builders switch to a high-shear-stability synthetic 5W-40 oil (such as Motul 8100 X-cess or Pentosin) to maintain oil film thickness under extreme turbo boost and heat.
- Oil Certification: Always look for oils meeting the API SN or API SP standard with ILSAC GF-6 specs to ensure compatibility with your emissions equipment and direct-injection fuel system.
You can verify official fluid requirements directly through the Subaru Owner Support Portal or reference certified lubricant guides on CarAndDriver.
Tools and Parts Needed for an Oil Change
Gathering your supplies beforehand makes the job cleaner and faster. For a 2018 WRX, you'll need:
- 5.1 quarts of approved 5W-30 synthetic motor oil.
- An OEM Subaru oil filter (Part Number 15208AA160 or the upgraded black Japanese-market 15208AA128 filter). Avoid cheap aftermarket filters that lack the correct internal bypass pressure valve rating for turbo Subarus.
- A new crush washer for the oil drain plug (Subaru Part Number 803916010). Never reuse an old crush washer, or you'll risk slow oil leaks.
- A 17mm socket and ratchet.
- An oil filter wrench or pliers (the factory filter is often installed tightly from the factory or previous service).
- An oil catch pan and funnel.
- Clean shop rags and nitrile gloves.
Step-by-Step Oil Change Procedure
Unlike older EJ-series engines where the oil filter was buried underneath near the exhaust headers, the FA20F engine in your 2018 WRX places the oil filter right on top of the engine block near the passenger-side front. This makes filter changes remarkably clean.
1. Warm Up and Elevate
Drive the car for five to ten minutes to warm up the oil so contaminants flow out easily. Safely raise the front of the vehicle using a hydraulic floor jack and secure it with heavy-duty jack stands. Never work under a car supported only by a hydraulic jack. Ensure the car is level.
2. Drain the Old Oil
Locate the oil pan underneath the engine. Place your catch pan beneath the 17mm metal drain plug. Use your 17mm socket to loosen the plug counterclockwise, then carefully unscrew it by hand while pulling it away quickly to avoid getting hot oil on your fingers. Let the oil drain completely for 10 to 15 minutes.
3. Replace the Crush Washer and Plug
Inspect the drain plug threads, install a fresh copper or aluminum crush washer onto the plug, and thread it back into the oil pan by hand to prevent cross-threading. Torque it down using a torque wrench to 29 ft-lbs (39.2 Nm). Do not overtighten, or you will strip the aluminum oil pan threads.
4. Swap the Top-Mounted Oil Filter
Pop the hood and look near the front right of the engine bay to find the upright oil filter cartridge. Place a rag around the base to catch any minor drips. Unscrew the old filter counterclockwise. Ensure the old rubber O-ring gasket came off with the old filter and isn't stuck to the engine mounting base (double-gasketing causes massive oil blowouts).
Dip a clean finger in fresh oil and lightly smear it around the rubber gasket of your new Subaru filter. Screw the new filter on by hand until it seats snugly, then turn it an additional three-quarters to one full turn. Do not use a wrench to tighten the filter.
5. Fill with Fresh Oil
Remove the yellow oil filler cap on top of the engine. Insert a clean funnel and pour in 4.8 to 5.0 quarts of your chosen 5W-30 synthetic oil. Save the remaining fraction of a quart for future top-offs. Reinstall and tighten the oil filler cap securely.
6. Verify and Reset
Pull the dipstick and wipe it, then reinsert to verify the initial level. Start the engine and let it idle for 30 seconds while checking underneath for any leaks around the drain plug and filter. Verify that the dashboard oil pressure warning light turns off immediately. Shut down the engine, wait five minutes for oil to drain back into the pan, and take a final dipstick reading, adjusting the level if necessary.
Common Mistakes to Avoid
Avoiding simple errors during maintenance protects your boxer engine from premature wear:
- Reusing the Crush Washer: Reusing old washers leads to uneven sealing and slow oil leaks that can empty your pan over thousands of miles.
- Over-Torquing the Drain Plug: The oil pan is aluminum. Overtorquing strips the pan, requiring a costly replacement or thread-repair insert like a Time-Sert.
- Using Non-OEM Filters: Aftermarket filters with incorrect internal bypass pressures can starve your turbocharger of oil during cold startups.
- Failing to Monitor Consumption: Turbocharged Subaru engines naturally consume small amounts of oil (up to one quart every 1,200 to 1,500 miles under spirited driving). Check your dipstick every time you fill up with gas.
Frequently Asked Questions
How often should I change the oil in a 2018 WRX?
Subaru recommends changing the oil every 6,000 miles or 6 months for normal driving. However, if you drive aggressively, track your car, or experience frequent stop-and-go city traffic, cut that interval down to 3,000 to 3,750 miles to protect your turbocharger and prevent oil breakdown.
Can I use 0W-20 oil in my 2018 WRX?
No. While modern naturally aspirated Subarus run on 0W-20 for fuel economy, the 2018 WRX turbo engine requires the thicker thermal protection of a 5W-30 oil. Using 0W-20 under high boost can lead to oil shearing and bearing failure.
Why is my 2018 WRX consuming oil between changes?
Direct-injection turbocharged boxer engines operate under high internal cylinder pressures. Minor oil consumption through the PCV system or past piston rings during heavy boost is normal for this platform. Check your oil level weekly to catch low levels before damage occurs.
What should I do if I accidentally overfill my engine oil?
If you added too much oil and the dipstick reads significantly above the upper dot, do not drive the car. Excess oil causes the crankshaft to whip the oil into foam, reducing hydraulic pressure and lubrication. Drain a small amount out by loosening the drain plug slightly or using a fluid extractor pump through the dipstick tube until the level normalizes.
