Parts for your 2018 Subaru Forester-Oil cap

2018 Subaru Forester oil cap — purpose, care, and replacement

Based on technical references including the 2018 Subaru Forester Owner’s Manual, Subaru service literature for the FB-series petrol engines, and the Subaru genuine parts catalogue, the 2018 Forester is fitted with an engine oil filler cap. It’s a necessary part of the lubrication and crankcase ventilation system, mounted on the cam/rocker cover under the bonnet. So yes, the oil cap is absolutely relevant and used on this model.

The oil cap’s main job is to seal the oil filler opening while allowing easy access for topping up oil. That seal does more than keep dust and grit out, it helps maintain the correct crankcase pressure and supports proper PCV (positive crankcase ventilation) operation. With a good cap and intact rubber seal, oil stays where it should, vapours are managed correctly, and the engine bay stays clean. Pop the cap off and it’s also the clearly marked spot to add the right-grade engine oil when servicing.

If the cap is damaged, loose, or missing, oil can splash out onto the engine, belts, and exhaust shielding, leading to mess, a burnt-oil odour, and potential belt slip. A poor seal can also allow unmetered air into the crankcase, upsetting ventilation flow and—on some setups—impacting idle quality. That’s why a healthy cap and seal are part of routine servicing for a 2018 Forester, whether it’s a petrol FB engine or the diesel variant.

Good practice is to inspect the cap at each service interval (typically every 10,000 km or 6 months, or as per the local schedule). Check the cap body for cracks or warping and make sure the rubber O-ring isn’t flattened, torn, or perished. Wipe any sludge off the threads and sealing surfaces. Fitment is simple: place the cap squarely and tighten by hand until snug—no need to swing on it. If the cap feels stuck, use a rubber glove for grip rather than tools that could crack the plastic. After any replacement, start the engine and confirm there’s no weeping around the cap and that there’s no unusual vapour escape.

• Replace the cap or O-ring if there’s visible damage, persistent weeping, fuel or heat hardening of the seal, or if it won’t seat firmly.
• Use a genuine or high-quality equivalent cap specified for the 2018 Forester to ensure the correct seal profile and venting design.
• Always refit the cap immediately after topping up—driving without it can quickly fling oil out and create larger issues.

Popular questions about 2018 Subaru Forester oil caps

Where is the oil cap on a 2018 Subaru Forester?
It’s on the top of the engine under the bonnet, typically on the right-hand side of the rocker cover for the FB-series petrol engine. It’s a clearly marked cap that says “Engine Oil,” designed for easy access when topping up.

What are the signs the oil cap needs replacing?
Look for oil mist or weeping around the cap, a flattened or cracked rubber seal, a cap that won’t tighten snugly, or a persistently oily smell after driving. Any visible damage or poor fit is reason enough to replace it.

Is it safe to drive without the oil cap?
No. Even a short drive can fling oil out of the filler opening, make a mess of the engine bay, and risk low oil level. Stop, refit or replace the cap, and only then continue driving.