Thermostat Mahle or Wahler

I've had a Wahler fitted for 1.5yrs and everything's ok so far

Spend slightly extra and get a quality OEM Wahler thermostat.

If you want hotter with a thermostat the exact same shape as the genuine VW version, get the Mahle TX1392D. 92 C opening temperature. Keeps the engine warmer and you get a little better fuel economy.

I replaced my newly bought Wahler t-stat with my old Mahle but drilled. Temps stays 80-87c.

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.

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.

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

I had two Wahlers and they leaked as soon as I fitted them. In exactly the way you described.

I got the wahler one in 2019, that would explain the really slow leak I have.

My Wahler thermostat starts to leak after 4 years. It's not a big leak (only a cup a month) but I'd swap it asap.