I had posted a few weeks ago that I was averaging about 17.5 MPG with my
2006 Chevy 5.3 liter pickup. All this week It seemed that I was putting an awful lot of gas in the truck. Yesterday I was sitting in traffic and noticed the temperature gauge was reading 180 degrees. Usually it shows 200 degrees. Seemed strange as I had been driving for over 30 minutes and sitting in traffic for 10 of those minutes. When the traffic let up and I was moving again, the temperature dropped to 170 degrees right away. Bingo, that's my mileage issue. The thermostat had stuck open and was not allowing the motor to come up to operating temperature, so the computer was keeping the fuel mixture too rich. Took it to the dealer this morning, they verified the bad thermostat, replaced it and now it runs at 200 degrees again.Brian