I have a 2001 GMC Jimmy 4x4 2dr with a 4.3L Vortec. I work for the local pizza place in my town and so i deliver pizzas and whatever else we have all around town. My fuel mileage absolutely sucks. I dont open the truck up or drive it hard in town or anything. On the highway i only get around 14-16 mpg and it seems to get like 8-10mpg in town. I have a new airfilter, spark plugs, spark plug wires, whole new distributer set up with cap and rotor bug and distributor. Is there anything i can do to improve the gas mileage any.

 

I feel your pain. I have been battling poor MPG's ever since I bought my blazer. Here's the best advice I can give you.... You could spend hundreds of bucks trying upgrades, chip burns, cold air intakes, plugs and so on - OR - take all that money, hit craig's list and buy the ugliest POS honda or toyota for under 500 bucks. Drive the crap outta it and hopefully get 20+ to the gallon and when you get home from working park it, then jump in the blazer for some fun. Oh yeah don't forget to hit walmart for some duct tape and bailing wire for those roadside repairs when the POS dies when delivering.

On a different note: You should be getting better than 8-10 in city. Even on my worse run I was getting 12 in the city. I would start with the basics. Get and ohm meter, timing light and maybe a fuel pressure gauge and start checking~

 

well i know my O2 sensor is bad but that really wouldnt make the mileage bad, would it?

 

If you are getting an engine code for a specific O2 sensor then I would check and clean the connector, check for broken wires, reset the code and see if it comes back. Well, O2 sensors, report to the computer the oxygen both up and down stream. So yes it could be faulty, causing an improper fuel mixture. Lets see if I got this right, upstream sensor checks to see if the mixture is within spec and the downstream sensor checks to see if the cat is doing its job.