W126 gasoline. Running cool all the time. Never gets over 50C. Must be that the stat is open. This doesn't really bother me except that perhaps it might run a tad rich and become less fuel efficient, but I haven't noticed that. Started in the summer and it seemed to be a good thing then. So is this the 'fails open' (would be smart design) normal design or otherwise stuck not closed? Never overheated. Besides a gasket and a new stat, do I need anything else when I replace this?