Maruha 78°C Thermostat · NA / NB Miata
Maruha's lower-temperature thermostat — opens at 78°C vs. the OEM unit's higher setting. Crucially, it also features a larger valve diameter (approximately 31.5mm) and a longer stroke (10mm) than the stock thermostat, maximizing coolant flow once open. This is not just about opening temperature — it's about how much coolant can flow when it does open.
Technical Details (from Maruha Motors Japan):

Opening temperature: 78°C (lower than OEM)
Valve diameter: approximately 31.5mm — larger than OEM for increased flow
Stroke: 10mm — longer than OEM for better flow volume
Keeps engine running cooler under hard driving conditions
For 1.6L NA6: must be used with Maruha Water Temperature Sensor Adapter (sold separately)
For 1.8L: compatible directly or with Maruha sensor adapter

Fitment: NA and NB Miata MX-5 · All variants. Note: NA6 1.6L requires Maruha Water Temperature Sensor Adapter for correct gauge reading.
Made in Japan. Authorized Maruha import by Chikara Motorsports — North America's only official Maruha dealer.