Parts for your 2020 Mazda 3-Oil cap

2020 Mazda 3 Oil Cap — Purpose, Care, and When to Replace

Technical sources confirm the 2020 Mazda 3 (BP series, Skyactiv‑G engines) is fitted with a conventional engine oil filler cap. The Mazda 3 Owner’s Manual (Engine Oil section) instructs drivers to “remove the oil filler cap” when topping up, the BP‑series Workshop Manual (Lubrication System) diagrams show the cap on the rocker cover, and Mazda’s electronic parts catalogue lists an “Oil Filler Cap” for BP‑chassis engines. So yes—this part is absolutely relevant to the 2020 Mazda 3.

On this model, the oil cap does two simple but vital jobs: it provides the access point for adding oil and it seals the top of the engine to keep contaminants out and oil vapours in. That little seal helps maintain proper crankcase breathing and stops oil mist from coating the engine bay. If it’s missing, loose, or perished, expect oily smells, splatter under the bonnet, and a mess around the cam cover.

As part of routine servicing, it’s worth giving the cap a quick once‑over. Check the rubber seal for hardening, cracks, or flattening. Make sure the threads aren’t cross‑threaded and that the cap turns smoothly and seats fully. A light wipe of the area around the filler neck before removing the cap keeps grit out of the engine. When refitting, go hand‑tight only—snug and seated, no need for tools. If the cap is stuck, a clean cloth for grip usually does it. Any ongoing oil misting or a cap that won’t hold tension is a cue to replace.

Replacement is straightforward. Opt for a genuine Mazda BP‑series oil filler cap or a high‑quality equivalent with an integrated seal that matches the Skyactiv‑G filler neck profile. It’s not a part that wears out on a schedule, but it should be replaced if the seal is tired, the cap is warped, or if it’s been lost or damaged. A fresh cap helps preserve oil quality, protects the engine from dust and moisture, and keeps the bay tidy.

Quick checks under the bonnet between services—oil level, any signs of dampness around the cap, and that the cap is properly seated—go a long way. It’s a small part that quietly prevents big headaches.

Popular questions about the 2020 Mazda 3 oil cap

Where is the oil cap on a 2020 Mazda 3?
The oil cap sits on the top of the engine, front and centre under the bonnet, usually marked “Engine Oil” with a small oil can icon. It’s a twist‑off cap on the rocker (cam) cover, easy to spot once the engine cover is lifted or viewed from above.

Can driving with a loose or missing oil cap cause damage?
Yes. A loose or missing cap can let oil splash out and allow dust or moisture in. That can lead to oil smells, visible smoke off hot components, and a messy engine bay. While it might not trigger a warning light straight away, it should be corrected immediately to avoid contamination and oil loss.

How often should the oil cap be replaced?
There’s no set interval. Replace it when the rubber seal is brittle or cracked, if the cap won’t tighten properly, or if there’s persistent oil misting around the filler area. Otherwise, a quick check at each service is all it needs.