TC lockup / milieage help

[stockSHO233]

I just read some threads on TC lockup, mileage, and engine temp and have just a few questions.
My car: The last 10 tanks has gotten 190-210 miles to the tank, and I don't drive it hard at all. I rarely go over 3000 RPM's solely because of how bad mileage it's getting.
I think it's running cool, I'm not sure where the gauge goes exactly. This may be because my thermostat went out last year and it has been since the new one. I'll check later today, but I know the high guess would be maybe the L. That's the high.
And the TC doesn't lock up unless I turn off and turn back on - but I hear that's common.

My multiple questions:
How exactly would I go about fixing my TC lockup / engine running to cool?
-I think maybe my therm may be a 170 one? Should I get a new thermostat? I don't think they're expensive.
I just ordered the ACCEL supercoil, new sp wiring, and have plugs all getting put in next week. What would be next in line for me to get to improve milieage? 10-12 is really hurting me with premium, and 3.50 gas!

I'm just looking for an order that I should do things. Thanks guys!

 

[SHOZ123]

You can put an oil t-stat in the tranny cooler lines. I had to do this on my '97 to get the ATX fluid temp up in the winter. It's not the engine temp that determines when the TC locks but the ATX fluid temp.

http://www.perma-cool.com/Catalog/Cat_page14.html

These will keep the fluid at ~185F after a driving a while. I may have to bypass it in the summer though.

 

[SHOZ123]

You should have a ~190F t-stat as this is what you need for the best mileage. Along with a cooling system that doesn't leak and holds pressure.