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.
This Part Fits:
| Year |
Make |
Model |
Submodel |
| 1989-1993 |
Dodge |
D250 |
Base |
| 1989-1993 |
Dodge |
D350 |
Base |
| 1989-1993 |
Dodge |
W250 |
Base |
| 1989-1993 |
Dodge |
W350 |
Base |
⚠️ California Proposition 65 Warning:
This product may expose you to chemicals known to the State of California
to cause cancer or reproductive harm.
The AutoHouse Advantage: Global sourcing power paired with specialized expertise. We utilize an expansive supply network of over 600,000 SKUs to deliver world-class components with an enthusiast’s precision.
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Price Match Guarantee:
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We are committed to providing the best value. If you find a lower advertised price from a verified vendor, we will match it. Shop with confidence knowing you’re getting the industry's lowest price.
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Project Incentives:
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We reward enthusiasts who trust us with their major projects. Use these tiered codes at checkout to apply instant savings to your order:
• AH25 — $25 OFF $500+ | • AH60 — $60 OFF $1000+
• AH180 — $180 OFF $3000+ | • AH400 — $400 OFF $6000+
• AH630 — $630 OFF $9000+
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Fitment Guarantee:
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Avoid the headache of the wrong part. If you are unsure about compatibility, contact us first. If we verify the fitment for your vehicle via email and it doesn’t fit, we will handle the exchange at no cost to you.
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Secure Shipping:
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We offer FREE Ground Shipping within the 48 contiguous United States. Most in-stock orders process within 48 hours. For your security, high-value performance parts require a signature upon delivery to ensure they reach you safely.
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Unused items in brand-new, original packaging can be returned within 30 days. While standard refunds incur a 25% restocking fee, we will waive this fee entirely if you choose store credit or an exchange for your next upgrade.
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Exclusions:
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To ensure every customer receives brand-new, untampered components, parts that have been installed, modified, or used are non-returnable. Custom builds, special orders, and wheel/tire packages are considered final sale.
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Need assistance? Reach out via our
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Fitment Guarantee
Fitment guides and tools are helpful—but your car is unique! Some trims and options aren’t always listed, so if you want 100% confidence that a part will fit, our team is happy to double-check for you. We take the guesswork out of your purchase by standing behind our expertise.
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Verify Your Build:
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If this product doesn't list your specific vehicle data, simply reach out to support@autohousesupply.com. We will manually verify compatibility for you.
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Our Promise:
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When we confirm a fitment in writing and it doesn’t work for your application, we cover the return shipping and exchange it at no cost to you.
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