I suppose I should have qualified that by saying Autos should stay with the proper (is it 95*? ) thermostat - it can cause transmission control to play up - or I should say I've SEEN it cause transmission to play up - on 3 different cars over 10 years.

In a braod sense it's actually inefficient to run the engine too cool.

I drive 5 speed... I think its 97deg thermostat stock.
I can see it stuffing up autos but I havnt had a problem with it. But I probably am running it too cool and loosing some efficancy.