Parts for your 2020 Subaru Legacy-Thermostat

2020 Subaru Legacy Thermostat — What It Does and How to Look After It

Technical sources confirm the 2020 Subaru Legacy is fitted with an engine coolant thermostat. The Subaru Service Manual for 2020MY Legacy/Outback (Engine Cooling section), the Subaru Technical Information System (STIS), and OEM parts catalogues for FB25 (2.5L) and FA24F (2.4L turbo) engines list a thermostat assembly located at the water pump/lower radiator hose outlet, with an opening temperature around 88°C. So yes, a thermostat is absolutely relevant on this model.

On a 2020 Subaru Legacy, the thermostat is a small but critical valve that manages coolant flow to keep the engine at its sweet-spot operating temperature. When the engine is cold, it stays closed so the motor warms quickly, once it reaches roughly the set temperature, it opens to route coolant through the radiator and stop things getting too hot. That stable temperature helps fuel economy, keeps emissions tidy, and protects the engine from thermal stress.

While thermostats aren’t a routine “time-based” replacement item, they do wear. For a Legacy doing regular kilometres, it’s smart practice to assess the thermostat during cooling system services—especially when replacing coolant, a radiator, water pump, or hoses. Subaru’s blue long-life coolant typically has extended change intervals (often up to 11 years/220,000 km for factory fill, then at shorter subsequent intervals), and checking the thermostat performance at those milestones is good insurance.

• Common signs it’s on the way out: slow warm-up, heater blowing cool air, temperature gauge creeping or fluctuating, radiator fan running excessively, or overheating under load.
• Best time to replace: alongside a coolant change or water pump job to save labour and gasket costs.

When replacing, use a quality, correct-temperature thermostat and a fresh gasket/O-ring, then refill with the specified Subaru-compatible coolant. Bleeding air properly is crucial on the flat-four—air pockets can cause hot spots and false overheating. After the job, a road test and scan-tool check of coolant temperature (ECT) data helps confirm proper opening and stable temps.

Owners who maintain the cooling system—clean coolant, sound hoses and cap, and a healthy thermostat—give the Legacy’s FB25 or FA24F engine the best chance of long, trouble-free service. It’s a small part doing an outsized job, and looking after it pays off.

• Checkpoints during servicing:
  • Inspect for leaks and corrosion at the thermostat housing.
  • Confirm warm-up time and steady operating temperature.
  • Pressure-test the system if overheating or fluctuation is noted.

Popular questions about 2020 Subaru Legacy thermostats

Does the 2020 Subaru Legacy have more than one thermostat?

It uses a single primary engine coolant thermostat in the outlet/housing near the water pump. Some models also incorporate separate control strategies via the ECM and electric fans, but there isn’t a second mechanical thermostat for the engine coolant circuit.

How often should the thermostat be replaced on a 2020 Legacy?

There’s no fixed kilometre interval. Replace it if there are symptoms (overheating, slow warm-up, temp swings) or preventively when tackling major cooling work like a water pump or radiator replacement. Many owners consider preventive replacement somewhere past the 150,000–200,000 km mark, especially if doing a full cooling-system refresh.

What temperature should the Legacy’s thermostat open at?

Factory specification for the 2020 model’s thermostat is around 88°C opening temperature, with full opening several degrees higher. Exact data is listed in the Subaru Service Manual for the 2020MY Legacy/Outback.