Fuel Mileage went down!?!?
 

I have a 2001 GMC Z71 extended cab 4x4. I used to get about 17.5-18.5 on mostly highway driving. Now I am getting about 15 at the most, and I even tried driving with the cruise at 64 most of the time. I have changed the plugs and wires as well as the fuel filter. The truck has a K&N open air, a dual exhaust, TB spacer, and just programmed it witha FlashPaq tuner to the 87 octane program. The truck was pretty much all stock when the truck was getting the better mileage. The truck seemed to get a drop in mileage after the exhaust, plugs & wires, fuel filter, and the programming. Im confused here. What kinda mileage should I be getting and what would cause the drop im MPG?? Any help would be appreciated. As well, is there anything I can do with the FlashPaq to help?

RE: Fuel Mileage went down!?!?
 

I know SMOKE20 from the chevy fourm had a issue with his mpg and he cleened his filter and maf sensor and then ran a few day and cleaned the maf sensor again and it helped. Just be carefull when you clean it. It has small metal sensors that will break easy. Hope this helps. Thanks

RE: Fuel Mileage went down!?!?
 

I did see that GM dealerships have a fuel system cleaning for $120, not sure what all it involves. Has anyone tried this, any success??

What kind of mileage do you guys get out of 5.3L 4x4's??

RE: Fuel Mileage went down!?!?
 

Im guessing thats the injectors getting cleaned and yes if you have highmileage it will help. I would not go to the dealer you can get it done buy a oil change place for alot cheaper. But i would still clean your maf sensor if you have not done so already.

RE: Fuel Mileage went down!?!?
 

I just read a FlashPaq and it recommends a higher octane than 87. All I can say it reprogram to a higher octane and give it a try to see if it improves. Keep us posted.

Ruben

RE: Fuel Mileage went down!?!?
 

The programmer dumped more fuel...

Mo' power = Mo' gas