Hi, I have 2008 chevy 2500 express van 4.8L with 110,000.
I noticed that my fuel economy was down from 10.5mpg to 8.5mpg in matter of 2 weeks.(500 miles driven )
Every week 1mpg lower.
No changes to driving habits,correct tire pressure, no excessive idling, no repair ,except for 2 news tires and an wheel alignment and state inspection .
Car sounds the same, runs the same.No check engine light.
I changed the air filter , but no tune-up was performed.
Should I do basic tune-up ,wires,rotor+cap,sparkplugs ,possibly a fuel filter or take it to the mechanic to check the sudden drop in mpg. Could worn parts that i’m planning to replace by doing tune up cause such fast drop in mpg? I follow MPG daily , as it is displayed as default on my dash.
When a sudden drop in fuel mileage occurs, the first two things checked are a thermostat that’s stuck open, or a faulty coolant temp sensor for the computer.
In your case it would be plugs, wires and heatshields . . . no cap and rotor, your van doesn’t have a distributor. Rather, it has 1 coil per cylinder. Each plug has its own dedicated ignition wire and heat shield. The wires and heat shield tend to get all buggered up, when you remove them. Especially the heat shield. If you’re going that route, replace everything, or you’ll be sorry
It was a gradual decrease , i would say 0.1MPG a day while driving about 30miles a day.
Could it still be thermostat or faulty coolant temp sensor problem ?
Could be a thermostat . . . is the engine taking an abnormally long time to reach proper operating temperature
Are you living somewhere, and the filling stations have already switch over to the next season’s fuel?
Are you absolutely sure the parking brake isn’t perhaps partially engaged? No offense, but it’s quite possible to have a bad parking brake switch, and the red brake lamp will not come on, when you have the parking brake pedal depressed
I believe your door jamb says 50psi front, 80psi rear . . . that’s what you’re doing, correct?