Parts for your 2020 Mazda 3-Oil seals

2020 Mazda 3 Oil Seals — What They Do and When to Replace

Oil seals are absolutely fitted to the 2020 Mazda 3 (BP series). Technical sources confirm it: the BP Mazda3 Workshop Manual contains procedures titled “Crankshaft Front Oil Seal Replacement”, “Rear Oil Seal Replacement” and “Drive Shaft Oil Seal Replacement”, and the Mazda Electronic Parts Catalogue for the BP chassis lists crankshaft, camshaft and transaxle oil seals for Skyactiv‑G 2.0/2.5 models with both 6‑speed auto and 6‑speed manual gearboxes. So yes—oil seals are relevant parts on this vehicle.

On a 2020 Mazda 3, oil seals keep engine and transmission fluids where they belong while keeping dust and grit out. They sit around rotating shafts—think the front and rear of the crankshaft, the ends of the camshafts, and the transaxle’s drive‑shaft openings. A thin, spring‑backed rubber lip rides on a machined surface to hold pressure and hold back oil. When they’re healthy, you won’t notice them, when they’re tired, you’ll spot weeps under the bonnet, around the bellhousing, or near the driveshafts, and maybe smell hot oil on the exhaust after a drive.

They’re not a scheduled service item, but they should be inspected at each service. Common clues include dampness around the crank pulley, oil mist inside the under‑tray, a drip from the bellhousing weep hole (rear main), or greasy build‑up where the shafts enter the transaxle. A slow drop on the dipstick or transaxle fluid level is another tell. Causes are usually age and heat, a worn groove on the shaft running surface, or excess crankcase pressure from a blocked PCV/breather.

Replacement advice for a Mazda 3 BP is straightforward: confirm the leak source first, then use genuine or high‑quality aftermarket seals. Lightly oil the seal lip, press it in square to the specified depth, and inspect the shaft for wear. It’s smart to renew related one‑time‑use fasteners and seals (e.g., crank bolt, timing cover sealant, axle circlips) and to check the PCV system so the new seal isn’t forced to leak. Front crank and cam seals usually mean accessory belt and pulley removal, the rear main is a gearbox‑out job, so many owners time it with a clutch (manual) or trans service. Driveshaft oil seals require popping the shafts, so fresh transaxle fluid is often part of the job. Fresh, correct‑spec engine oil, not overfilled, and regular services will help seals live longer over the kilometres.

• Watch for fresh oil near the crank pulley, bellhousing, and drive‑shaft stubs.
• Fix crankcase ventilation issues before fitting new seals.
• Plan seal work with related maintenance to save labour and downtime.

Popular questions about 2020 Mazda 3 oil seals

Where are the most common oil seals on a 2020 Mazda 3?
The big ones are the front crankshaft seal (behind the crank pulley), the rear main seal (between engine and transmission), the camshaft seals (behind the cam gears on the timing side), and the transaxle drive‑shaft oil seals where each driveshaft enters the gearbox. All are documented in the BP Mazda3 Workshop Manual and listed in the Mazda EPC.

How often should oil seals be replaced?
There’s no fixed interval. They’re replaced on condition—when they leak or during related work that provides easy access. For example, it’s common to do a rear main seal when the gearbox is out, or a front crank seal during timing or front‑end engine work. Regular servicing and a healthy PCV system help them last.

Is it okay to keep driving with a small oil‑seal leak?
Short term, many owners do. But leaks can worsen, contaminate the timing belt/aux belts, clutch, or rubber mounts, and lead to low oil levels. It’s best to monitor the level closely and book the car into a favourite workshop sooner than later—especially if there’s oil on the exhaust or the leak rate increases.