Parts for your 2010 Subaru Legacy-Sump plug washers

2010 Subaru Legacy Sump Plug Washers

Based on technical sources — the Subaru Service Manual for the 2010 Legacy/Outback (Engine Lubrication section) and the Subaru Genuine Parts Catalogue — the 2010 Subaru Legacy does use a sump plug washer (also called a drain plug gasket). Subaru specifies an aluminium crush-type washer, genuine part number 11126AA000 (commonly superseding the earlier 803916010) fitted to EJ25 and EZ36 engines used in this model year. The service manual also notes reinstalling the drain plug with a new gasket and a tightening torque of about 43 N·m.

For this model, the washer’s job is simple but critical: it crushes slightly as the plug is torqued up, conforming to any tiny imperfections between the plug flange and the sump. That creates a reliable, leak-free seal without needing sealants or tape. It also helps spread the clamping load so the alloy sump isn’t marked or distorted — a big win for long-term reliability.

Subaru’s service information calls for replacing the crush washer every time the oil is drained. They’re inexpensive, and fresh aluminium seals far better than a flattened, work-hardened old one. When the washer is reused, it may not crush properly, leading to weeping or that annoying drip on the driveway. For owners across Australia and New Zealand who do their own servicing, keeping a couple of spares on hand is a smart move.

Handy servicing pointers for this Legacy:

• Use the correct-size washer (Subaru’s aluminium 16 mm crush washer as per the parts catalogue).
• Clean the sump’s sealing face before refitting — no sealants or PTFE tape needed.
• Torque the plug to around 43 N·m, don’t “gorilla” it. Over-tightening can distort the sump face or strip threads.

Tell-tales that a washer needs attention include a damp film around the plug after an oil change, a visible groove in a reused washer, or evidence of over-tightening. If any of that shows up, swap the washer and re-torque the plug correctly. Whether the car runs the 2.5 or 3.6, sticking with the genuine-spec aluminium crush gasket keeps servicing tidy, the sump sealed, and the engine happy.

Popular questions about 2010 Subaru Legacy sump plug washers

What size is the sump plug washer on a 2010 Subaru Legacy?
Subaru specifies an aluminium crush washer with a 16 mm inner diameter for this model. The genuine part number commonly used is 11126AA000 (which supersedes 803916010). Always match by VIN if unsure, but this size and type is standard across the 2010 Legacy range.

How tight should the sump plug be?
Subaru’s service manual lists around 43 N·m for the drain plug. Fit a new crush washer, clean the mating face, and use a torque wrench. Over-tightening can mark the sump or damage threads, under-tightening risks weeps, so aim for the spec.

Can a copper washer be used instead of aluminium?
Aluminium is the factory call-out and is preferred. A soft copper washer of the correct dimensions can seal, but it may require different crush characteristics. If copper is used, it must be new (or properly annealed) and the right size. For hassle-free servicing, stick with the Subaru aluminium washer.