I have a old white rogers thermostat and trying to hook it to a Honeywell RTH2310. When I have taken the cover off my old thermostat it only has 4 wires. The diagram for the Honeywell shows a 5 Wire.

I have Blue, White, Yellow and Gray

Old stat: - White Rodgers
System: - ? I will need this info like is it Gas furnace or heat pump
Efficiency of furnace if it is furnace- ?
Wires: - 4
Terminals Wired:- I will also need the terminals that were used on your old stat like R,G,Y,W,