The OEM stat is a 4 pc. design and a quality US design is 1 pc. Why not use a quality 1 piece design stat? Help me understand why the 4 pc is better design. I see that some 1 pc have the air bleeder at top also.

 

Having struggled to put the 4-piece together, the only answer I can give is that it promotes the virtue of patience.

Maybe I've lived a sheltered life, but I've never seen a build-your-own thermostat before.

Probably more to the story ...

 

due to Limited Response, further research indicates the Lincoln LS 3.9L has a similar stat (4 pc) and was not able to locate others sharing this design. One would presume the Super Coupes and Other Fords using this engine series would also share this stat. Discovered a study by 4 Clemson U. professors detailing different types of cooling systems and stats. No mention of 4 pc. stats in their study. Apparently the secret to the 4 ps. will remain in question.
Automotive Thermostat Valve Configurations for Enhanced ...

Page Not Found | Clemson University, South Carolina University

 

My guess is that one manufactured part (or several parts, in this case) can be used in many different styles of plastic or metal housings provided by various vendors. Not very user friendly, however.