Parts for your 2017 Subaru Outback-Sump plug washers

2017 Subaru Outback sump plug washers — yes, they’re used

On the 2017 Subaru Outback, a sump plug washer (also called an oil drain plug gasket) is definitely used. Technical sources that confirm this include the Subaru Factory Service Manual for 2015–2019 Outback/Legacy (Lubrication section) and the Subaru Genuine Parts catalogue, which list an aluminium crush washer for the engine oil drain plug, part number 803916010 (16 mm). Both the 2.5i FB25 and the 3.6R EZ36 engines specify fitting a new washer each time the plug is removed. The factory tightening spec is about 44 N·m, as noted in the manual’s engine oil change procedure.

What does the washer actually do? It’s a soft, single-use ring designed to “crush” slightly as the drain plug is tightened, sealing the joint between the sump and the plug. That crush action prevents weeps and drips without needing sealant, and it means the correct torque achieves a reliable seal rather than relying on brute force. Try to reuse a flattened washer and there’s a fair chance of a slow seep, or you might overtighten the plug to chase a seal and risk damaging threads in the alloy sump — not a fun fix.

For servicing a 2017 Outback, swapping the washer at every oil change is cheap insurance. Use a quality aluminium crush washer sized for the Subaru plug (M16), and clean the sump face and plug head before reinstalling. Fit the new washer, snug the plug, then torque it to the factory spec. After the first start, have a quick look underneath to confirm it’s bone dry.

How to spot a washer that’s due for the bin? If it’s visibly gouged, coned, or already pancake-flat, replace it. If there’s even a light film of oil around the plug after a drive, fit a new washer and retorque correctly. Avoid stacking washers, and skip thread tape or liquid sealants — Subaru’s own guidance is to use the crush washer only.

• Washer type: aluminium crush, single-use
• Size: M16 (Subaru p/n 803916010)
• Tightening: about 44 N·m to factory spec

These details reflect Subaru’s workshop procedure and parts listings for the 2017 model year Outback, ensuring a tidy, leak-free service every time.

What size sump plug washer does a 2017 Subaru Outback use?

It uses an M16 aluminium crush washer. Subaru’s genuine part number commonly supplied for this model is 803916010. A quality aftermarket M16 aluminium crush washer is fine if it matches the OEM dimensions.

Do you have to replace the washer at every oil change?

Yes — it’s a single-use crush gasket. Subaru’s workshop procedure specifies installing a new washer any time the drain plug is removed to ensure a proper seal at the correct torque.

Does the washer have a correct way up?

The genuine Subaru aluminium washer is symmetrical, so orientation isn’t critical. If using an aftermarket washer with a distinct chamfer or stepped face, put the flat side to the sump and the chamfered side to the plug head.