I am running 87 octane with as low of an ethanol content as possible here. I have no warning lights. I haven't checked the spark plugs. Cargo area is empty. I try to only let it idle when stopped at a light or in traffic. Checking the plugs may be my next move if this oil change didn't improve it michelle thank you.

I have both the instant and avg on the DIC. That statement was just a round about guess from watching the instant. So far after changing the oil today I saw about 33 MPG or higher (just guessing again) on a 15 mile straight stretch of 55 MPH highway. I think the oil level may have been the culprit.

 

OK. Straight to the point. DO NOT use the instant mpg for doing any type of gas mileage calculations. It is just that. For that instant. Take your foot of the gas and coast. It will say as high as 99 mpgs.
Point being. Unless your brain can calculate like a computer and average all those "instant" readings over a long haul, then the instant reading is of no use in determining real gas mileage.
Only thing instant is really good for is maybe to monitor your driving habits, such as acceleration rate mpg or maybe best cruise speed for mpgs.
Not trying to belittle anybody with my comments, so please don't take it that way.
It would have been better if GM would have just left this little instant mpg thing out of the system.

 

Yes my 2008 2LT has both also.......... I don't really ever use the 'instant' mode tho..

 

I always take the DIC readings with a grain of salt, the best way to track your mileage is the way Grandpa did, grab a pencil and a piece of paper. Or keep a fuel log, just jot down what, where, and how much, then you can track your mileage over a longer sample time.

 

The oil has been changed and refilled with the proper amount of 5W30. I took a trip today of 280 miles, most of which was 60 to 65 mph the rest was about 75 miles was at 70 to 80 mph. Once home I am at above half a tank and the dic average economy is at 33.5. I was running the recirculated air about 80% of the trip also. Much better economy and more to my liking.

 

I hope things will remain on the up and up with your fuel economy. Please, let me know how things are going later next week. I hope you have a great weekend planned.

Michelle, Chevrolet Customer Service