Well my mpg has gone way down.My average went from 17 down to 12 in the last month.I was sitting in the parking lot this morning and watched it go from 12 to 8.7.When I drive it goes back up a little,bout 13 avg.It doesn't drive any different,no smoke,no lights.I'm at a loss.Anyone have any ideas?

 

it's from your foot. still enjoying the blackbear tune i see.

 

yeah I enjoy it sometimes now that I can put premium back in it.But this last tank I have been taking it real easy and it looks like I'll get around 250 for this tank.I mean I still get 20 on the highway,so I don't know somethings gotta be off somewhere.Its not the tune,I noticed it goin down slowly before even the headers..

 

Maybe your o2s are going bad.

 

+1 on the o2's

 

Sitting in the parking lot staring at it won't tell you anything. Your burning gas and going 0 mph will equal 0 mpg which lowers your average.

But other than that I'll 3rd the o2's. I got about 230 to the tank when one of my o2's went out.
go ahead and get a new air filter and fuel filter tho.

 

this might not have anything to do with it but are you running ethanol in your gas?

 

i run 10% ethanol and it never affected my mpg

 

no I just run 93 premium.

I have my rear o2 sensor laying in the garage.Are they all the same?.

I was getting 19-21 on average on the interstate today,so now I'm really stumped.20 on the highway and 10-11 in town babying it

 

was just curious about the ethanol. If you have the average mpg show up on dash in the DIC. one thing to remember if you go off what the on-board computer says. It is always calculating if you are stopped or driving. In park or drive. My wife has an equinox and says she gets 12 mpg around town. Granted there are stop lights here and there but she has no lead foot either. And speaking of o2 sensors. I dont know how they run with out them, but my 2001 silvy did not like the simulators. I fouled plugs like crazy.