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The 6.4L Powerstroke (2008-2010 Ford Super Duty) runs a dual-thermostat setup, so every real replacement here is sold as a kit of two thermostats, not a single unit. That doubles the part count and the price versus a typical single-thermostat gas engine — a fact that has already tripped up pricing on this site once, on the sibling 6.0L fan clutch and thermostat articles, which quoted gasoline-engine prices for diesel-specific parts. These are the actual OEM and aftermarket kits sold for the 6.4L today, all priced as complete 2-thermostat kits.
| # | Product | Price | Where to buy |
|---|---|---|---|
| 1 | Motorcraft OEM Thermostat Kit (8C3Z-8575-D / RT-1212) | $99-$110 for the 2-thermostat kit | Amazon · eBay |
| 2 | Alliant Power Thermostat Kit (AP63498) | ~$105 for the kit | Amazon · eBay |
| 3 | Mishimoto Low-Temperature Thermostat Set (MMTS-F2D-08L) | ~$100-$101 for the set of 2 | Amazon · eBay |
| 4 | Mishimoto High-Temperature Thermostat Set (MMTS-F2D-08H) | ~$99-$100 for the set of 2 | Amazon · eBay |
The picks, in detail
Motorcraft OEM Thermostat Kit (8C3Z-8575-D / RT-1212)
The factory Ford part — the reference point every other kit here is measured against, and the safest choice if you want exact OE behavior.
- OEM Ford/Motorcraft part number 8C3Z-8575-D
- Includes both thermostats + housing gasket
- 2-year Motorcraft warranty
- Guaranteed correct OE calibration
- Widely stocked by Ford parts dealers and diesel shops
- Not the cheapest option available
Alliant Power Thermostat Kit (AP63498)
A direct OEM-equivalent kit from Alliant Power, a major diesel OEM-parts supplier, cross-referenced to the same Ford part number.
- Alliant Power part AP63498
- Cross-reference to OEM RT1212 / 8C3Z-8575-D
- Includes both thermostats
- OEM-equivalent quality from an established diesel parts brand
- Comparable price to Motorcraft
- Slightly less brand recognition than genuine Ford/Motorcraft
Mishimoto Low-Temperature Thermostat Set (MMTS-F2D-08L)
A performance option that opens at a lower temperature than stock, aimed at owners who tow heavily or run in hot climates and want more cooling margin.
- Set of 2 low-temperature thermostats
- Direct-fit replacement
- Designed specifically for the 08-10 6.4L application
- Extra cooling headroom for towing or hot-weather driving
- Reputable performance-parts brand
- Not a stock-behavior replacement — changes warm-up characteristics
Mishimoto High-Temperature Thermostat Set (MMTS-F2D-08H)
The stock-equivalent-temperature version of Mishimoto’s 6.4L thermostat set, for owners who want the brand’s build quality without changing warm-up behavior.
- Set of 2 high(stock)-temperature thermostats
- Direct-fit replacement
- CNC-machined housing compatible
- Closer to stock thermal behavior than the low-temp version
- Good fit and finish
- Priced similarly to OEM despite being aftermarket
Buying tips
- The 6.4L Powerstroke (2008-2010 only) uses TWO thermostats in the housing — always buy the 2-thermostat kit, never a single unit.
- Do not confuse 6.4L parts with 6.0L or 6.7L Powerstroke thermostats — the housings and part numbers are different despite similar-sounding forum threads.
- Replace the housing gasket every time regardless of which thermostat kit you choose — it’s a one-time-use gasket.
- If you tow heavily or live somewhere hot, a low-temperature thermostat set (like the Mishimoto low-temp) buys extra cooling margin; otherwise stick with a stock-temperature OEM or OEM-equivalent kit.
As an Amazon Associate and eBay Partner, toptenpick.com earns from qualifying purchases. Prices and availability are subject to change.