I have a 99 model Dodge Ram 2 wheel drive, 3.9 six-cylinder magnum engine and AT. It has around 86K miles on it. In the 3 years I have owned the truck, the temp guage indicator never gets above 160 degrees. I got to to thinking that this might be affecting fuel mileage. I've never checked the mileage, but I know it isn't very good. Theoretically, would it be more efficient at the 195-200 degree temperature? Any thoughts? Thanks.

Sounds like the thermostat is stuck open...you might replace it and see if that gets you to normal operating temperatures.