Originally Posted by OXlvsMPR85
Well that all makes sense... we all did not buy these trucks for the mileage, but i drive it mostly on the highway. I do however need my timing cover, and plenum gaskets replaced. While that's all apart I'm going to replace the thermostat and O2 sensor and see how we do after that.
I will tell you that with new O2 sensors you MAY see slightly better IF they are bad. Honstly those dont go bad that often unless you are running the engine rich
As far as the thermostat goes. Buy an OEM one. If you get one that runs the engine colder (or warmer) than the OEM spec are...you WILL get horrible gas milage. Running a "cooler" Thermostat will hinder performance by not allowing it to reach proper operational temp to properly burn A/F mixture...along other emission issues it will cause also tearing up MPG efficiancy. The old-timers sayin that running a cooler or colder thermostat will help your engine last is a myth and will eventually destroy your engine.