I'm debating whether or not to pick up a Derale adjustable fan regulator that will turn the radiator fan if the car reaches 200 degrees. I was going to purchase the device until the salesman behind the counter told me it will increase my gas consumption.

Is this true?

Will it harm my engine if I never let it get above 200 degrees?

It is quite alright to run over 200. I don't think you'll need that fan.

We never run the GTP over about 170 degrees, and it seems to run pretty decent. (decent meaning only low-mid 12'*) With the electric water pump it has, in normal operating conditions it never gets over 160 degrees. The thermostat opens at about 158 according to the autotap, and the engine cools down to ~152 before it closes again. It is only at WOT that it goes higher than ~160. We haven't had any problems yet, and it definately performs well still. It MAY hurt gas mileage, but I can't see it hurting it more than 1mpg or so. Also, it isn't going to hurt the engine to run 220 degrees either.

Shawn