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.
I used oem bmw coolant and a mahle thermostat.
I have an 06 Audi A3 2.0T Sportback with just over 105k miles; recently replaced the thermostat, spark plugs and coil packs. Other than being in need of some new brakes and a bit of cosmetic love, she's running strong.
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.
Recently had the exact same issue on a 14 a6 ended up being a DOA t stat I compared the shaft length on the new t start to the 2nd new t stay and sure enough it protruded out about a mm further just enough to not seal properly causing the over cooling after the swap no more issues.
Had this happen to our 2018 Q5 a few months back, 35k miles on the SUV. Thermostat issue plus some other stuff.
Hatte auch schon ein Mahle Thermostat das kurz nach eimbau defekt war. Dannach ein Originales von BMW rein und seit dem wi3der keine Probleme.
Last week changed the thermostat on my 1.9 tdi 66kW to a Mahle TX 15 87D (11€), it was fine for the first two days, then the temps started dropping again.
1st Mahle. The engine only reaches up to 65 degrees and it drops further if I drive under 2000RPMs on highway for example or turn on the heating.
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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 OEM Audi were overall better than Mahle.
Thermostat OEM Audi and Mahle were equally popular according to data in March 2026.
By vote balance, thermostat OEM Audi surpassed Mahle:
By number of reviews, thermostat Mahle surpassed OEM Audi:
In March 2026, according to PartReview, thermostat Mahle led more car-specific ratings than OEM Audi:
Mahle are chosen by owners of cars such as: Jeep Grand Cherokee, and others.
Thermostat OEM Audi 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 OEM Audi with: MotoRad, Wahler, OEM Volkswagen, OEM Mazda, MOPAR, MISHIMOTO, Gates, OEM BMW, OEM Nissan, OEM Honda.
Also available: comparisons of thermostat Mahle with: MotoRad, Wahler, OEM Volkswagen, OEM Mazda, MOPAR, MISHIMOTO, Gates, OEM BMW, OEM Nissan, 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.
