Capown

iTrader: (5)

Not sure what section to post this in.. I have a 06 Silverado 2wd Crewcab, shortbed w/5.3. 182k miles I don't dog my truck and normaly have a light foot as the MPG already sux so I don't try to make it worse. I've put new plugs and wires fuel filter, and a new MAF after I replaced the MAF MPG on the cluster said 21.5 for a day or so then fell off back to 13-15. When I bought the truck I calculated out Gallons used to Mileage and it was 17.5mpg. WTF is making it suck soo bad now?? I also have a Tune from a local guy it's no bueno and I alway run premium since I got it. If I don't it pings alot!

Rebob5

iTrader: (3)

My 09 silverado ext cab 4x4 with the 5.3 and 30k miles on the clock in 2wd gets around 15.3 highway miles per gallon and I drive 55 miles per day to work. My old 01 silverado with the same specs as my newer one gets right around 14 mpg. I did just recently replace plugs/wires/coil packs,air cleaner and did a fuel system cleaning on my 01 and that picked it up from around 12mpg to the 14mpg it gets now.

01WS6/tamu

iTrader: (37)

Flash it back to stock and start there for diagnostic purposes. If that improves it call black bear or nelson they are sponsors here and get a tune from them. You can probably be expecting to have a set of plugged cats with that many miles and that can kill power and gas mileage but a exhaust shop can do a simple back pressure test on them to determine if they are flowing correctly.

lt1pwr1

iTrader: (1)

My first suspicion is that tune you have. That could be causing all your problems.

However, if that is spot on then I would consider replacing your front o2's. Those can have a very large effect on gas mileage and with 180K on the clock, they could probably use replacing.

Just get some from Amazon or Rockauto - get the Denso brand and nothing else.

Capown

iTrader: (5)

Thanks for the replies I'll get the cats checked and lookinto the o2's.