I use Nulon Red since I found out that many places dont
warranty anything with Tectalloy. Ive used Tectalloy in
previous cars with no dramas but heard several owners
had thermostats issues similar to Micks description.
I only found out about the red when I went to buy some
as recommended by MBenz manuals but fell over backwards
when I found the price and went Nulon Red instead.
Maybe someone with more insight can dime in.