Thermostat OEM Mazda or AISIN

Hard to say if it’s directly OE to Subaru, but I use Aisin thermostats and water pumps on every Subaru engine I do, they function the exact same and are equally as reliable as the original equipment, not to mention these thermostats are $15 on amazon compared to $40 from Subaru.

I had the same issue on my 09 Mazda 2.3L. Everything looked good on the dash, but the thermostat let too much coolant through, over cooling the engine. My CEL came on, I reset it, and it reappeared. Long drives on the freeway in cool weather was the scenario that triggered it, as the radiator is very effective at speed, and the engine isn't working hard cruising on level ground at freeway speeds. I bought the thermostat "cover" (it's the plastic assembly with the thermostat integrated in it-- PN LF70-15-170) for $57 from Amazon and installed it last November and the CEL has not reappeared.

After doing some research I found that AISIN is likely the supplier for the Subaru OEM thermostats so I ordered them off of Amazon (sold and shipped by Amazon) and they appear to be just that. They were close to the same price and are made in Japan. AISIN THF-007/009 appear to be true OEM Subaru thermostats for FB20B

Pick up the AISIN OEM version of your thermostat. It's pretty cheap so no reason not to get the best one instead of some cheaper alternative. Also you can test the function of your thermostat before doing the change by putting it in hot water. You can check the specs of the one you use, but for the AISIN one for my 2012 civic (9th gen), the thermostat starts opening at 170 and is fully open at 190.

I still changed my thermostat to an Aisin unit for peace of mind, so far so good.

Common for the thermostat and/or coolant control valve to fail on newer Mazda 3s. It's not a big deal but you might have more coolant loss and it takes longer to warm up.

My 2021 Mazda3 Turbo has classic thermostat failure symptoms: \n\n- Erratic warm-up (sometimes stuck cold, sometimes near overheating). \n- Upper radiator hose stays lukewarm even after 20+ mins of driving (revved to 3K RPM to test). \n- Housing burns hot, but hose never gets scalding\u2014clear sign of a stuck thermostat.

That's due to their faulty thermostat for which they don't want to assume responsibility and call it what it is - a recall.

Aisin THF-003 thermostat was used (I believe this is what I'm regretting). It's like the thermostat isn't opening? Everything else seems fine - it's clearly getting hot. Little to no heat at idle. No circulation = overheating of the engine. Is the replacement thermostat stuck shut?

Our 2022 CX-5 Premium Plus (non turbo) is going in for its 3rd thermostat replacement next week. Each time it’s been replaced at Mazda under warranty with an OEM part. Vehicle will hit 90,000 Miles this month. Does this thermostat wear seem excessive or is it normal for these? Bought brand new and it’s been the only problem, other then general maintenance