Lower v6 gas mileage than usual. What to check?

[crewxp]

I have a 2010 2lt RS camaro. I used to average around 21/22 mpg city. And that was with a heavy foot, enjoying my car.

For the past month or so I have been averaging 15/16mpg. I Drive the same places and am even accelerating a LOT slower than I usually have in the past. I see no change in mpg.

I was wondering if something might be wrong. What should I check? My oil was last changed in January at 12k miles. I am at 16.5k miles now in July. I brought it in for an oil check, but they told me I am only at 38% remaining oil life and didn't need it yet. So I guess that's not the issue.

Any suggestions? I've never had to fill up this much before

[TJ91]

no clue but very interested in his

[bkscott]

Check your gas 1st. If they switched to a mix with ethanol, it could cut your mileage.

[Cymaro]

I have the same problem. Right now at 100% city driving I'm getting 12-13mpg using 89 octane 10% ethanol.

[Sidd218]

I thought the V6 didnt go under 18mpg?

[SC2150]

Good info in some of the posts above. First thing is the gasoline. If you were using a non ethanol brand and have now started using an ethanol mix your economy can suffer as much as 2-3 mpg as the ECM will adjust the fuel delivered based ont he information from the MAF, MAP, and upstream O2's.

The other thing is if you have not been running a catchcan that catches the majority of the oil that is ingested into the intake air charge, you probably have substantial carbon/guk buildup on the valves, piston tops, and combustion chamber that will result in loss of power & fuel economy. The heat dosent help with the power either.

To check to see if this is the case use a boroscope to look into the cylinder through a spark plug hole while the intake valve is open and you can see the build up.

I suspect you have a combination of all the above. The proper oil separating catchcan (only a few actually catch all or nearly all the oil, but any is better than none) will prevent the build up and pay for itself many times over.

[seddon]

like stated above it could the gas mix at your station. Also I have noticed due to a little heat wave in NYC and most of the USA higher ambient temps affect my gas mileage and I also have the ac cranking.

[seddon]

also just because your oil life reading says 38% it has been 6 months I would change it. I average about 6k miles a year and do 3 oil changes a year, not needed but safer.

[LessSinister]

I'm surprised no one has said check your tire pressure yet.

[drex1999]

I live in a smallish town with hills. No hwy driving normally. I am and have always averaged 15 MPG.

[Cymaro]

This past week the heat index has been between 102 and 115 in my area and I have my a/c running. Tire pressure is 39 for all corners. But my highway mileage has been spot on with 27.5mpg running 89 octane 10% ethanol, and when I have switched to 87 octane no ethanol in the past on the highway I get 31 mpg on my trips to my other home.

[Cymaro]

And also I let my car high idle before I put it in gear every time I start it up. I don't know if anyone else does this, but probably doesn't help.

[angie7]

Originally Posted by Sidd218

I thought the V6 didnt go under 18mpg?

I wish! That's the best I have ever gotten in mine! I average 16 in town and 18 on the hwy. Its my fault tho, I have a major heavyfoot at take off and just having fun on the roadway. One big reason why I passed on the v8, didn't need the extra $$ gone and trouble with the law

[TooCool5]

Originally Posted by crewxp

I have a 2010 2lt RS camaro. I used to average around 21/22 mpg city. And that was with a heavy foot, enjoying my car.

For the past month or so I have been averaging 15/16mpg. I Drive the same places and am even accelerating a LOT slower than I usually have in the past. I see no change in mpg.

I was wondering if something might be wrong. What should I check? My oil was last changed in January at 12k miles. I am at 16.5k miles now in July. I brought it in for an oil check, but they told me I am only at 38% remaining oil life and didn't need it yet. So I guess that's not the issue.

Any suggestions? I've never had to fill up this much before

I would check your rear exhaust pipes, should be shiny clean inside or you are running rich. Air filter or bad 02 maybe?
Important to zero you MPG readout at highway speed and see if the highway numbers are coming in. That will tell you it its running right.
I usually go from 35 MPG down to 33 on the highway. 35 psi in the tires.