Thermostat Wahler or OEM Mazda

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.

Spend slightly extra and get a quality OEM Wahler thermostat.

Got the Wahler on my 2008/2011 and it was identical to the MB part except the area that had the MB logo on the original one was ground out.

I've had the thermostat on my M272 engine replaced by an indy mechanic. OEM was Wahler, looking at the original the the Wahler I got, the only difference was the spot where the MB logo was on the original, it was grounded out by some grinding disk on the replacement one.

Always buy the Mazda OEM branded thermostat from any local or online Mazda factory parts retailer, this is not the item you want to save a couple bucks on, no matter how much you trust that ‘other’ brand.

My 2007 MKV 2.5 Jetta is still having overheat problems even after changing the tstat to a OEM (Wahler) and the waterpump to one with metal impeller, which works way better than the original.

My tstat is wahler. People said that it was better than Mahle. But I found it similarly poor.

Thermostat failed multiple times

Thermostat was ALSO replaced when the water pump was, with a Wahler unit. Guess I got 10k miles out of it?

I just had the code P0126 on my 2021 mazda cx-30 with 20,000 miles. Seems to be the same issue