Thermostat ?

[emolina]

I have the SOHC 4.0 L with 77,000 miles and the original thermostat. How do you know when your thermostat is stuck open?
At 88 degrees ambient temp. it took almost 5 minutes of stop and go driving before it even got close to its normal position (the needle barely at the thermometer icon). Does this sound ok?
Truck runs great but my mileage doesn't even come close to Aldive (about 12.5 over last 3 tanks)
Thanks for any help.

 

[marragtop]

I'd go ahead and replace it. It's an easy fix and part of normal maintenance. Just be glad that it's sticking open. If it's sticks closed, you're hosed.....