I believe the thermostat in my 02 Disco II is going bad. Even though the engine is warm, the heater won't come on for 20-30 minutes. The fans work properly. Where's the best place to order one?

Also I'm going to do an oil change while I'm at it. What type of oil do you all use in the winter? It seems like I remember some people use a different type in cold weather.

 

could be a thermostat stuck open, could be your heater core is restricted, also could be your coolant level is low from a leak. Winter oil, if you like synthetics Rotella T6 5w40 or mobil 1 5w40 TDT are great oils. If you prefer conventional then use a 5w30 pennzoil and valvoline are good, motorcraft 5w30 semisyn is great too.

 

How many miles on your truck, where do you live and how cold does it get?
Be specific, how long after the temp gauge show normal operating temp, does it take for the heat to come up? Also, when cold, where is your coolant level?

 

You can get a thermostat for it at AutoZone.