It may have been the gas. I've put two different brands in since the poor performance and the gas mileage is working its way back up.

The performance boost came off the line. More a feeling than anything. And I don't floor it, LOL! In fact I try to drive a bit under the speed limit to help conserve fuel.

As far as hauling around unnecessary stuff, the only thing in the back is a Kelty kids backpacker. God help me if that 5 lbs is killing my gas mileage.

Still, if running mainly on Interstate, below the posted speed limit of 70 here in WV, I was hoping for better than 12 MPG. Hills or no hills.

- mike

 

BTW, all of the tune-up stuff was AC Delco. Factory wires and factory iridium plugs. Now the gap was .040 instead of the original .060, but Chevy says that is ok, as the .040 plugs supercede the .060 plugs.

- mike

 

Hmmm weird. Maybe change the gap back to 60 and try that. It could be bad gas as stated by others.

 

No, the gap is supposed to be at .040. You can't gap those plugs without damaging them.

There may be another reason for the gas mileage drop. I'll know by the end of the week and update.

- mike

 

Oh ok i understand now. Let us know what you find. Were all interested.

 

did u ever figure out the probloem i have a 01 tahoe with the same probloem did a tune up and then a severe drop in gas mileage had it at the garage and they say everything checks out catalytic conv,o2sensors,injectors,fuel mixture, and they did a power test on it and passed ata total so any help would be appreciated thank u

 

The air filter can cause this, especially if he replaced with a fancy k&n air filter. You get better performance but you pay for it at the pump

 

It was the gas. I've been averaging 18 MPG ever since. A bit higher when driving on Interstate, but I'm usually loaded down for vacation with my family of 6. I usually run 87 in it, but will run 89 occasionally. I've never run 92/93 in it.

 

FWIW, premium gas will not improve mpg (unless engine actually tuned for it) or it is E-0.

 

Is this ethonol or real gas, big difference in the two