2007 Chevrolet Silverado 1500 - 50% fuel economy reduction

Maintenance/Repairs
1

My 2007 Silverado has recently lost approximately 1/2 of it’s fuel efficiency. No check engine light. Any guidance would be greatly appreciated.

Thanks,
Scott

2

Did you change tires or wheels? Colder temperatures lower fuel economy. Have you changed driving habits? How are you determining your fuel economy?

3

A thermostat that’s stuck open will cause a drop in fuel mileage.

Or, the coolant temp sensor for the computer is telling the computer the coolant never reaches operating temperature when it actually does.

Tester

1 Like
4

Thanks for the quick response.

I am watching the automatic MPG measurement on the dash… and plus I can tell on how fast I am going through gas… no changes in driving approach.

So the truck has the auto V4 to V8 mode and it is a challenge to keep it on the V4 mode and rarely goes to V4 mode. I have a cheap ODBII monitor and was looking at short term and long term fuel trims and they seem to be cumulative 0 when adding together. What I did notice is that one of the O2 sensor seems to be slow to react and appears to stick (not as active as the other 3) is it possible that the O2 sensor is bad.

I also do require a fuel pump as I have a long crank and usually just turn the key to the on position and for a couple seconds prior to starting…

I hope this additional info helps…

5

Hi Tester, thanks for helping…

I have not noticed the temperature gauge dropping out to not normal temps and my truck does put out very good heat…

Also more info:

So the truck has the auto V4 to V8 mode and it is a challenge to keep it on the V4 mode and rarely goes to V4 mode. I have a cheap ODBII monitor and was looking at short term and long term fuel trims and they seem to be cumulative 0 when adding together. What I did notice is that one of the O2 sensor seems to be slow to react and appears to stick (not as active as the other 3) is it possible that the O2 sensor is bad.

I also do require a fuel pump as I have a long crank and usually just turn the key to the on position and for a couple seconds prior to starting…

I hope this additional info helps…

Scott

6

It’s certainly possible that you have a bad O2 sensor, or some other issue. You mention a lot of variables going on simultaneously.

It concerns me a bit, the manner in which you’re “measuring” your fuel economy. The onboard dash reading can be a bit misleading at times.

If it were me… I’d measure mileage between fillups divided by total gallons. Do that for a few fillups, and see what your actual MPGs are. Compare that to (I assume) other data from the past as a reference. That will give you a true picture of whether or how much your MPGs have changed. Go from there.

1 Like
7

Very good points, I will take your advice to be more confident about my actual MPH and try to continue to evaluate my other metrics I had referred to.

Thanks