In this video, I'll be testing some various engine cooling thermostats to see if they open at the correct temperature. I've noticed a trend with Duralast thermostats (manufactured by MotoRad out of Israel), and it's not exactly a good trend. In 2014, I replaced the original OEM thermostat in my Jeep Grand Cherokee 5.2L because it was starting to weaken and not open up enough when hot outside. Before it started failing, it was good at maintaining a constant temperature. I chose to pick up a thermostat from AutoZone. Upon installing this thermostat, I noticed on cool days that the dash gauge never seemed to get as hot as it should. The old OEM thermostat made by RobertShaw kept the engine coolant temperature right at 210° whether it was 20° outside, or 90° outside. Refer to the images at 29:24 for a comparison of dash gauge readings between the factory OEM thermostat, the MotoRad (Duralast), and the Stant SuperStat. With the Duralast thermostat installed, the gauge would oftentimes "hunt" between the position in the left image, and the 210 mark, especially in the summer. That's because the cooling system on this vehicle was intended to keep the engine at 195°, not 180°. During warm days, it was not uncommon for the fan clutch to engage more often, as the cooling system was working harder to try to maintain 180°. That's right... the Duralast unit was opening up at only 180° despite being marked as "91°C/195°F". In late 2015, I replaced it with another thermostat just like it. I tested out both the 1st one and the 2nd one on the stove side by side. The 2nd one opened at 195° like it was supposed to. All seemed well... however within a month of installation, it too was opening at 180° like the 1st one 😡 I ended up running it like this for 4 years. As temps started getting cold out this fall, I noticed that it seemed like the Jeep was taking longer, and longer, and longer to warm up... While my Jeep's ECM didn't set a code for low operating temperature, some cars WILL set a check engine light code because of this. This past Friday, I replaced the 2nd Duralast Thermostat with a Stant SuperStat 195° thermostat from NAPA. So far, this thermostat is maintaining temperature similar to that of the OEM RobertShaw unit. What's funny is I've heard that the "OEM" thermostats sold at your local Chrysler Stealership, are just MotoRad units in a Mopar package. I performed the stove test with both Duralast thermostats again. This time the 2nd one was opening at 170°F 🤔 Definitely not 195°! On modern cars, the ECM expects the engine to warm up to a specific temperature. When it doesn't, fuel mileage will decrease, and engine wear can increase. as mentioned, in some cases when the temperature never reaches a specific point, the ECM may light up the check engine light and set the code P0128 - Coolant Temperature Below Thermostat Regulating Temperature. It seems like Stant SuperStats are the clear winner here. And Amazon sells them for about the same price as the "budget" thermostats from the parts stores. The MotoRad thermostats just seem to not want to open at their rated temperatures, and instead run cooler.
Another thing to note, when my mom was still driving her old Honda CR-V, she replaced the thermostat with a Duralast. That one also seemed to run the engine cooler than the OEM Honda thermostat before it failed! So that makes THREE Duralast thermostats that aren't performing within specified tolerances.
To wrap this up, I wouldn't recommend using Duralast (or Duralast Gold) thermostats from AutoZone, Murray thermostats from O'Reilly's, FailSafe Thermostats (also made by MotoRad), or any thermostat manufactured by MotoRad. Instead, pick up a Stant SuperStat on Amazon... or if you need to get it from a parts store, NAPA sells them. I also believe the CarQuest thermostats from Advance are Stant products.
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