DIY - Thermostat Install
 

Replacing the thermostat is one of the easiest, cheapest, and most imperceptible ways to increase fuel economy. Stock thermostats, which generally open at around 180 degrees, are a compromise between performance and fuel economy. If you're treating your engine kindly you can get away with installing a 195 degree thermostat in order to push your fuel economy up ever so slightly. Since most radiator fans will not turn on until a 210+ degree condition is reached, you should be fine under normal conditions.

Take a look at this graph relating fuel trim to engine temperature in Hondas. This offers some theoretical evidence of the savings, though it is generally so small that testing would be nearly impossible:
http://crxmpg.com/edrive-images-crxmpg-com/ECT.jpg

Purpose: A hotter engine runs more efficiently. By increasing the coolant temperature a few degrees we can improve the efficiency of the engine very slightly.

Time: 30 minutes

Tools:
- Socket Wrench
- Basic Metric Socket Set
- Pliers

Supplies:
- 195 Degree Thermostat
- Thermostat Gasket
- Coolant to replace that which you spilled

1. Take a look at your damn engine compartment. Find the thermostat housing. It's in the middle of this picture, with the big hose going to it:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00106.JPG
2. Get your pliers on the big clamp, move it off, and take off the big hose going to the thermostat:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00107.JPG
3. Take the one side of the housing off (two 10mm bolts) and expose the thermostat.
http://crxmpg.com/edrive-images-crxmpg-com/DSC00108.JPG
4. Yank the old thermostat out with some pliers. Now you realize where all the spilled coolant will come from!
http://crxmpg.com/edrive-images-crxmpg-com/DSC00109.JPG
5. Put the gasket or new gasket on the new thermostat.
http://crxmpg.com/edrive-images-crxmpg-com/DSC00110.JPG
6. Put the thermostat back in and replace the housing. Tighten it down not to much, but just enough. Torque specs help!:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00111.JPG
7. Look at your completed work.
http://crxmpg.com/edrive-images-crxmpg-com/DSC00112.JPG

Note: I will likely be undoing the 195 degree swap in the future for various reasons, but still, here ya go.

Why would you need to undo the 195F thermostat?

Probably putting an electrical one so he can change the temperature when he wants? Just guessing.