I replaced my EGR awhile back. This last tank of 8 gallons was about 13 mpg. I usually keep it around 2-3 rpm on average. So im quite baffled.

 

Check your oxygen sensors?

 

Have you been regularly using fuel system cleaner like the Lucas one? I would use it at least once every other month, and for a few tanks in a row if you have never used it...

Also spray your TB butterfly valve with cleaner to clear any varnish build-up, switch to full synthetic oil for better gas mileage as well. Ensure you have good plugs & wires and no misfires.

Adding a CAI, lid, filter and removing the air resonator will also improve your mileage. Adding headers and a better flowing exhaust might also help.

 

Yeah, my car was getting poopy gas millage as well earlier this week. I bought an intake cleaning kit and some STP Fuel Injector Cleaners, its gas millage is a lot better now. Don't know the exact number, but I was getting about 180 miles to a full tank, now I'm getting a little over 200. I need to change my spark plugs too, that should help.

 

GMDCAMARO my buddy's 93 z 28 was about the same predicament we took it in to auto shop (our class) and unscrewed the front o2 sensor and played around with that to see if it got better. All in all try that and you may have a bad 02 sensor or a clogged cat. Just a thought not saying I'm right just a suggestion.

 

Ya, i've been meaning to check the O2's lately. Just haven't found time

 

Thanks for your suggestions guys, I think the first time I miscalculated, cause I filled up tonight and it seems I got roughly 17-18 mpg. I went about 150 miles on 8.6 gallons. So while I'm glad that's higher than I thought it still doesn't seem to be as good as possible. I'm putting in new spark plugs and wires one of these days so I'll see if that helps any.

 

Try sea foam. Half in your vacuum lines and half in your tank. Do a search to find the correct way of dong this and think you will be surprised.