Parts for your 2015 Subaru Impreza-Exhaust gasket

2015 Subaru Impreza exhaust gasket: purpose, service tips, and FAQs

Technical sources confirm the 2015 Subaru Impreza uses several exhaust gaskets. The Subaru Service Manual for 2015MY Impreza (FB20) in the Exhaust section specifies gaskets at the cylinder head–manifold joint and at the front pipe spring-bolt connection, instructing technicians to “always replace the gasket with a new one” once a joint is separated. Subaru’s electronic parts catalogue (often referred to as FAST) also lists multiple exhaust gaskets for this model, including the manifold-to-head gasket, the front “donut” gasket, and flat flange gaskets further downstream. So an exhaust gasket is absolutely relevant and fitted to the 2015 Subaru Impreza.

On this Impreza, exhaust gaskets seal hot gases at key joints so the system stays quiet, leak-free, and emissions-friendly. They also help the engine management maintain proper oxygen sensor readings, which keeps fuel economy tidy and avoids nuisance fault codes. Typical gasket styles on the FB20 include a multi‑layer steel (MLS) manifold gasket, a compressible metal/graphite donut gasket at the spring‑bolt joint, and flat flange gaskets at the centre and rear sections.

There’s no fixed replacement interval, but gaskets should be renewed whenever a joint is undone, and any time symptoms crop up. Subaru’s service literature calls for new gaskets and, at spring-bolt joints, new self‑locking nuts. Signs a gasket is on the way out include:

• A sharp ticking on cold start that softens as it warms
• Exhaust whiff near the front of the car, or soot marks around a flange
• Raspy note under load, drop in fuel economy, or catalyst efficiency codes if a pre‑cat leak is present

When servicing, allow the exhaust to cool fully. Inspect the manifold-to-head joint, the front pipe donut, and rear flanges for soot trails and corrosion. If removal is needed, replace the gasket(s) as a matter of course. Use OEM or high‑quality equivalents and follow torque specs and sequences from the service manual—cross‑pattern for the manifold, and correct preload on spring bolts at the donut joint. Avoid sealants