Subaru FB25 engine: known problems

The torque-converter CVT can shudder or judder at low speed as the lock-up engages, and some cars develop surging or hesitant take-up. Most low-speed judder is cured by a Subaru TSB software reflash. Outright CVT failure is uncommon but very expensive when it happens, especially on neglected cars.

FB-series boxers can use oil and develop leaks from the timing cover, cam carriers and head gaskets, with oil sometimes burning onto the exhaust. Consumption eased on 2015-on builds but some still drink between services.

A subset of FB25 engines burn oil through premature wear of the oil-control piston rings, with low oil-light or smoke between services. Affects roughly a small percentage of engines but is well documented and the subject of a Subaru TSB; severe cases needed updated rings or a short block.

Owners report a shudder under light load, a 'bump' or jolt at idle in Drive once the CVT is warm (Subaru TSB for 2015-17 2.5i), and a 1-4 second delay shifting reverse to drive. Most are nuisance-level and resolved by a TCM reflash and fresh CVT fluid; a minority escalate to valve body or full transmission replacement.

Some FB25 engines, mainly earlier-build cars, consume oil between services (a known issue that triggered an overseas class action on the related 2013-2014 cars). Most BS examples are improved over the launch engines, but a minority still use oil.

The CVT can show slow/jerky response, which Subaru addressed with a fluid change and ECU reflash. The BS unit is much better than the 2010-2014 cars, but neglected fluid shortens its life and replacement is expensive.

The front lower control arm bushes degrade and cause clunking over bumps and alignment drift - a common SJ niggle.

Carbon accumulates on intake valves and ports over time, causing rough idle or a slight loss of smoothness at high km.

Like most Subaru boxers, the FB25 can weep oil from cam carrier/valve cover gaskets and, less often, head gaskets at higher km.