Parts for your 2020 Holden Commodore-Sump plug washers

2020 Holden Commodore sump plug washers — what they do and when to replace them

Yes, the 2020 Holden Commodore uses a sump plug washer. Holden/GM Service Information for the ZB Commodore (Opel Insignia B platform) instructs fitting a new sealing washer with the engine oil drain plug at service. GM Genuine Parts/ACDelco catalogues list a dedicated oil drain plug seal for these engines (for example, GM 12616850, M14 seal) and drain plug assemblies supplied with an integral seal (for example, GM 11562588), and major aftermarket parts catalogues in AU/NZ also specify M14 sump plug washers for ZB 2.0T and 3.6 V6 variants. That technical guidance confirms the washer is relevant and used.

On the 2020 Commodore, the sump plug washer is the simple hero that keeps the oil in and the mess out. It sits between the drain plug head and the sump face, crushing slightly as the plug is torqued so it seals tiny surface imperfections. Whether the car’s running the 2.0‑litre turbo four or the 3.6‑litre V6, the principle’s the same: a fresh, correctly sized washer provides a reliable seal without having to overtighten the plug.

There are two common setups on these cars: a separate crush washer (usually aluminium or copper) used with a standard M14 x 1.5 plug, or an OE-style plug that has a captive, rubber‑coated sealing ring. In both cases, the washer or seal is considered a consumable. GM’s service literature calls for replacing the seal whenever the plug is removed, which in practice means at every oil change.

Why bother? Reusing a crushed washer can lead to slow weeps, oil spots on the driveway, or worse, the temptation to swing on the spanner to “stop the drip”, risking stripped sump threads. A new washer lets the plug be tightened to the correct specification (use a torque wrench and follow GM SI for your engine) and then forgotten about until the next service.

What to watch for:

• Dampness or grime collecting around the drain plug after a service
• Washer visibly gouged, deformed, or stuck to the sump face
• Plug removed for any reason between services

Handy tips for owners and techs:

• Use the correct size — most ZB Commodores use M14 x 1.5. Match the washer material and thickness to OE spec or a quality equivalent.
• Clean the sump sealing face and plug head before fitting the new washer.
• If using a plug with an integrated seal, replace the seal if serviceable separately, or the whole plug if the seal is damaged.
• Torque to the GM spec for your engine, don’t rely on “feel”.

Popular questions

Does a 2020 Holden Commodore need a new sump plug washer every service?
Yes. GM’s service guidance treats the washer as a single‑use sealing component. Replacing it at each oil change ensures a proper seal at the correct torque and helps avoid leaks or damaged threads.

What size sump plug washer fits the ZB Commodore?
Most ZB engines use an M14 x 1.5 drain plug, so an M14 washer of the correct thickness and material (commonly aluminium or copper) is used. Always confirm against the specific engine code and the old plug before buying.

Can the old washer be reused if it looks okay?
It’s not recommended. Crush washers deform to seal once, reusing them increases the risk of seepage. If the plug uses a captive rubber‑coated seal, replace the seal (or the plug assembly) if it shows flattening, nicks, or hardening.