Differences in Thermostats

[1988lx]

During this past cold snap (high of 26 F), I found myself wanting more heat than my festy was putting out.
using the ever handy "search" function, I found that the well versed festy guru's are recommending a two-stage thermostat as it came from the factory.
someone on here also said that Autozone carries one(Duralast part #41492) for a 1993 Mazda Miata that is just what the doctor ordered for around 10 bucks.
after tearing into mine, I found a generic 195 single stage....replaced that with the autozone unit.

Then I just got curious and pulled a few 'stats from engines I had laying around for Identification.

I can verify "B3H7" was factory installed in a 22,000 mile 1997 aspire that was a "parts virgin"....it is a SINGLE STAGE
(also found exact same single stage in a very un-loved high miles 1994)

However, I am not quite sure about "E5D3 NT" 2 stage that I found in a 1992 E.GT BP at 40,000 miles, I'm ASSUMING its factory installed as well
Lastly I found a two stage from a 1991 E.GT BP 157,000 miles, with ABSOLUTELY NO MARKINGS!! I'm thinking this one is a dealer replacement???? can anyone verify?

attached a few pics here to clarify : http://s885.photobucket.com/user/alabama1387/library/

Now im just waiting for the next batch of freezing weather to see if there's a difference.

[bravekozak]

The two stage thermostat will slow the flow of engine coolant slightly, since the holes are smaller. They are meant to maintain the coolant temperature within a narrower band. Although the two stage may provide a few degrees warmer temperature in winter, the single stage will be able to provide a few degrees cooler in summer. Let us know your findings.
A good analogy to this principle of operation is that of a digital valve.

[william]

I just picked up a 2 stage t stat from autozone tonight for my car I have a b6d but the stock b3 had a 2 stage in it.
but only the big one would open in a boil test.
I don't know how much this will help my heat or lack of it but I figured its cheap and worth a shot. I'll post my experience also.
Much colder here so ill get to use it right after installation .

[bravekozak]

You have a defective thermostat. The sub-valve should open (182°-188°F) before the main valve (188°-193°F). Both valves should be fully open at boiling (212°F).