I’ve installed Borg Wagner thermostats and those always failed until I installed a Mahle one which never failed. For some reason any other brand will get stuck open and the engine will never get up to temp.
I used Mahle, but I got lucky I got the German-made one (afaik now most are made in Italy). It was NOS so I expect the electrical heater (to open early) to be defect. It's been 3 years without issue though.
In the past and up to several months ago, I’ve always gone with Saleri (Italy) pumps and Wahler (Germany) thermostats for the M54 and have had great results.
I had a brand new mahle one with the connector wired in reverse for constant. Kept blowing a fuse. Returned it for a replacement and worked fine.
Mahle is an OEM supplier and is on stock in Amazon.
I recently changed the thermostat on my dad's car as well, I went with a wahler, and I'm observing the same things.
Hatte auch schon ein Mahle Thermostat das kurz nach eimbau defekt war. Dannach ein Originales von BMW rein und seit dem wi3der keine Probleme.
I decided to try another thermostat, this time a Wahler and nothing has changed as the car will still not get up to temperature and no hot air.
I changed on mine 2-3 months ago with a new one from Wahler/Borg Warner and now it's leaking through the connector.
I have experienced same with Wahler thermostat.
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If choosing thermostat across many manufacturers, check the part ranking. If your choice is down to two brands, the PartReview part comparisons help.
We compare thermostat across these categories:
In March 2026 on PartReview, thermostat Mahle were overall better than Wahler.
Thermostat Mahle and Wahler were equally popular according to data in March 2026.
By vote balance, thermostat Mahle surpassed Wahler:
By number of reviews, thermostat Wahler surpassed Mahle:
In March 2026, according to PartReview, thermostat Mahle led more car-specific ratings than Wahler:
Mahle are chosen by owners of cars such as: Jeep Grand Cherokee, and others.
Thermostat Wahler have not yet taken leading positions in car-specific ratings. You can help by adding a review and specifying your car.
If this comparison didn’t fully answer your question, there are many others on PartReview.
For example, comparisons of thermostat Mahle with: MotoRad, OEM Volkswagen, OEM Mazda, MOPAR, MISHIMOTO, Gates, OEM BMW, OEM Nissan, OEM Audi, Duralast.
Also available: comparisons of thermostat Wahler with: MotoRad, OEM Volkswagen, OEM Mazda, MOPAR, MISHIMOTO, Gates, OEM BMW, OEM Nissan, OEM Audi, Duralast.
You can also see who is better among other thermostat manufacturers: Wahler or MotoRad, OEM Volkswagen or MotoRad, Mahle or MotoRad, OEM Mazda or MotoRad, MOPAR or MotoRad.
