Parts for your 2017 Subaru Outback-Head gasket

2017 Subaru Outback head gasket — what it does and how to look after it

Yes, a head gasket is used on the 2017 Subaru Outback. Technical sources including the Subaru Factory Service Manual for the 2017 Outback, the Subaru FAST OEM parts catalogue, and well-known gasket supplier catalogues all list cylinder head gaskets for both engines offered that year: the 2.5‑litre FB25 flat‑four and the 3.6‑litre EZ36 flat‑six. These modern Subarus use multi‑layer steel (MLS) head gaskets between the aluminium block and aluminium cylinder heads.

On this Outback, the head gasket’s core job is simple but critical: it seals three things at once — high‑pressure combustion, engine oil passages, and coolant jackets. By keeping combustion pressure in the cylinders and fluids in their own galleries, it helps the engine produce power efficiently, prevents cross‑contamination, and keeps temperatures stable. When it’s healthy, you’ll barely think about it, when it’s not, you’ll see overheating, misfires, or fluid loss under the bonnet.

There’s no scheduled replacement interval for a head gasket — it’s a fit‑and‑forget part that should last the life of the engine if the cooling system is looked after. For servicing, the smartest preventative care is cooling‑system hygiene: run the correct Subaru Super Coolant (blue), keep the system bled, replace hoses and the thermostat when aged, ensure the radiator is clean, and fix any leaks promptly. Avoiding overheating is the single biggest favour anyone can do for a boxer engine’s head gaskets.

• Common warning signs: unexplained coolant loss, sweet smell or white steam from the exhaust once warm, oily “milkshake” under the oil filler cap, bubbles in the overflow bottle, rough cold starts, persistent overheating, or a heater that goes cold under load.

If replacement is required, most workshops prefer an engine‑out procedure on these boxer engines for access and accuracy. Best practice is to use quality MLS gaskets (OEM‑spec), follow the factory torque‑and‑angle sequence, check head and block flatness, and renew related seals and gaskets (cam carrier sealant, rocker covers, intake/exhaust gaskets). Many technicians also fit new head bolts and fresh spark plugs while they’re there, along with a new thermostat, fresh coolant, and engine oil. Expect it to be a major job — often a full day to two days of labour depending on whether it’s the 2.5 or 3.6 — and typically a several‑thousand‑dollar spend in AU/NZ workshops. A trusted mechanic will pressure‑test and sniff‑test the cooling system first to confirm the diagnosis before tearing in.

Treated well, a 2017 Outback’s head gaskets are far less drama‑prone than older EJ‑series Subarus. Keep the cooling system happy and they usually go the distance.

Popular questions about 2017 Subaru Outback head gaskets

Does a 2017 Subaru Outback actually have a head gasket?
Yes. Both the 2.5‑litre FB25 and the 3.6‑litre EZ36 engines use multi‑layer steel head gaskets. This is confirmed in the 2017 Outback factory service manual and OEM parts catalogues covering the cylinder head and gasket sets.

How long do the head gaskets last on a 2017 Outback?
There’s no set replacement interval. With proper cooling‑system maintenance and no overheating events, many run well past 200,000 km. Failures on the 2017 models are much less common than on older EJ‑series engines and are usually linked to overheating or neglected coolant service.

Should both head gaskets be replaced if one fails?
On a boxer engine, best practice is to do both sides while the engine is out. Labour is the bulk of the cost, and renewing both gaskets, related seals, and consumables at once helps avoid a second teardown later.