Parts for your 2018 Subaru Forester-Sump plug washers

2018 Subaru Forester sump plug washers — what they do and when to replace

Yes, the 2018 Subaru Forester uses a sump plug washer. This is confirmed by Subaru’s Factory Service Manual for MY2018 Forester (Engine Lubrication section), which instructs replacement of the drain plug gasket at each engine oil change, and by Subaru’s Electronic Parts Catalogue listing a replaceable aluminium crush washer for the engine oil drain plug (commonly 16 mm, part number 803916010, engine-dependent). Those technical sources make sump-plug-washers a relevant, fitted service item on the 2018 Forester’s FB/FA-series engines.

On this Forester, the sump plug washer is a soft, single-use crush gasket that deforms once when the plug is tightened. That controlled “crush” creates a tight, uniform seal between the steel plug and the alloy sump, preventing weeps and drips as the engine heat-cycles. It also protects the sump threads by providing a compliant layer, so the plug reaches the correct torque without over-stressing the alloy.

Best practice is simple: replace the sump-plug-washer at every oil change. Subaru’s service literature is clear about renewal, and it’s an inexpensive part that saves a lot of hassle. Fit a new OEM-style aluminium washer, clean the mating surfaces, start the plug by hand to avoid cross-threading, then tighten to the specified torque from the Subaru workshop manual for the exact engine code. Reusing a flattened washer risks under-sealing (leaks) or over-tightening (thread damage) as it won’t crush properly a second time.

Owners and techs should keep an eye out for tell-tales of a tired or re-used washer: light oil misting on the sump, a fresh drip on the undertray, or the odd spot on the driveway after a service. If any of that appears, a new washer and a re-torque to spec usually sorts it. Sticking with aluminium (as per Subaru) is wise, copper can work but may crush differently, and fibre washers aren’t recommended here.

As part of routine servicing, stocking a few spare OEM washers is a smart move for DIYers across Australia and New Zealand. Pair each oil and filter change with a fresh sump-plug-washer, dispose of used oil responsibly, and the Forester’s lubrication system will stay tidy and leak-free between services.

• Fitted component: Yes — replace at each oil change
• Typical type: 16 mm aluminium crush washer (verify by VIN/engine)
• Key benefit: Reliable seal without overtightening the sump

FAQs — 2018 Subaru Forester sump plug washers

Do all 2018 Subaru Forester engines use the same sump plug washer?
Most 2018 Forester variants (FB25 and FA20/FA20F where fitted) use a 16 mm aluminium crush washer. Part usage can vary by market and engine code, so the safest bet is to confirm via the vehicle’s VIN in the Subaru parts catalogue.

Can the sump plug washer be reused?
It’s designed as a single-use crush washer. Reusing it risks leaks or damage from over-tightening because it won’t deform correctly a second time. Replace it with a new OEM-style washer at every oil change.

What torque should the drain plug be tightened to?
Always use the torque spec in the Subaru workshop manual for the exact engine. Tightening to spec lets the new washer crush properly and seal without stressing the sump threads.