Mishimoto · New
Mishimoto 89-93 Dodge 5.9L Cummins 87.5C High-Temperature Thermostat
MPN MMTS-RAM-89H · Store SKU misMMTS-RAM-89H
Supplier stock checked 11/7/2026, 7:52:37 AM UTC. Adding a part does not reserve it.
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Product details
The 12-valve first-gen Cummins in your Ram is considered one of the best diesel engines ever produced, and for good reason. Fuel efficiency, torque, and simplicity are just a few characteristics that give the Cummins its stellar reputation. We're huge fans of the Cummins engine, which is why we've developed a high-temperature thermostat for the 1989-1993 5.9L 12v Cummins. This Mishimoto thermostat activates at a higher temperature (189.5F) compared to the factory thermostat (180F). By raising the activation temperature, coolant flows through the system later, promoting quicker engine warmup. The Mishimoto high-temperature thermostat is ideal for vehicles in cold climates, where rapid warmup and quicker in-cabin heat is vital. This thermostat includes a high-quality replacement gasket and our signature Mishimoto Lifetime Warranty. Engine coolant thermostat designed to regulate coolant flow and maintain optimal operating temperature. Ensures efficient warm-up, prevents overheating, and supports reliable performance with a precise fit. Thermostat, High-Temp, fits Dodge 5.9L First-Gen Cummins 1989-1993
Manufacturer fitment & guides
Check MMTS-RAM-89H against the manufacturer’s application information below.
Part-specific notes
- California Proposition 65: Y
