hey guys, just trying to figure this out so i can get it fixed.
My problem is lack of heat. When idling the car will warm up to roughly 200-220 degree'* and the car will blow warm air. However when i start driving the car the temperature goes down to 100-120 and it stops blowing warm air.

Is this due to the termostat which would also assist in the terrible gas mileage? (150 miles on first half, 70 miles on last half)

Sounds to me like the thermo is stuck open. They're cheap.

It would help with gas mileage by a handfull of MPGs if that'* the problem and you fix it. When it'* below the thermo temp, the PCM sends more fuel to try to warm it up.

Is it easy changing by yourself or just have the dealership do it? it would cost me around 70 bucks to have the dealer do it (I work at one)

Definitely an open stat. They are realatively easy to change.

Depending on your mechanical ability and which model/year you have it'* considered a snap.

The basic procedure is on a cool/cold car, drain off some coolant. Remove two bolts holding thermostat housing to the lower intake manifold. Clean gasket surfaces and remove old stat. Put in new stat, taking into consideration the filling procedure outlined in Techinfo, reassemble and enjoy the heat.

rizer, welcome to Bonneville Club. Please put the year and model of your car in your signature so we can help you with more accurate information.
I agree that your symptoms are consistent with a thermostat that is sticking partially open. However, your symptoms could also be caused by low coolant. With the engine cold, open the radiator cap - it should be full to the top. If not, you need to find the leak to make sure your problem isn't much bigger than no heat.

Welcome back, Chris.

If you want to save some $, I know you could change it yourself. If you want a hand or want to do it at my house, let me know.

Shouldn't take too long, if your radiator petcock will open to drain some coolant. If not, then you need to remove some coolant by a little more time consuming means.

T-stat is under $10. You may need to pick up a paper gasket if the stat you get doesn't come with one.

Stat won't come with the paper gasket.

And draining from the petcock takes me longer than the vacuum hose trick.

Thermostat
Rubber T stat gasket
Paper water outlet gasket

Chris..take Bob up on the offer..he'll even show you his cool hose clamp tool