ISR Performance Thermostat - Nissan VQ35HR & VQ37VHR - 68 Degree

The ISR Performance 68°C Thermostat for the Nissan VQ35HR and VQ37VHR drops the coolant temperature opening point from the factory 78°C to a colder 68°C. Standard cheap-insurance upgrade for hard-driven HR and VHR-equipped 350Z, 370Z, G35, and G37 builds. This is the VQ35HR/VQ37VHR variant without the water port. the older VQ35DE uses a different thermostat (IS-21200-31U13, with water port).

What It Does

The factory thermostat opens at 78°C, which is fine for emissions-cycle warm-up but leaves you closer to overheating territory once the engine is making real power. Opening at 68°C means coolant starts flowing through the engine sooner once it warms up, holding lower steady-state temperatures and giving you more margin before the gauge starts climbing. Useful on track days, summer driving, and forced-induction HR/VHR builds.

Fitment

Nissan VQ35HR and VQ37VHR engines (without water port) only. Will NOT fit the older VQ35DE. that uses the IS-21200-31U13 variant with the water port. Confirm your engine code before ordering. Typical applications: late 350Z HR, 370Z, G35 HR, G37, Q50/Q60 3.7L.

Product Details

Brand: ISR Performance

Part Number: IS-21200-31U03

Type: Cooler-temp thermostat

Engine: Nissan VQ35HR, VQ37VHR (without water port)

Opening Temperature: 68°C (vs factory 78°C)

Excluded: VQ35DE (use IS-21200-31U13)

Typical Applications: 350Z HR, 370Z, G35 HR, G37, Q50/Q60 3.7L

Application: High-performance HR/VHR builds, track use

Sold: Individually

Legality: Off-road and competition use only