hi, i just got done reading the MPG fuel mods https://www.truckforums.com/forum/si...mpg-mods-7108/ and have a few questions. i not only drive my '04 GMC Sierra 2500HD every day to work but i also tow. i am consistently getting about 12-13 mpg empty and about 8-10 mpg with a 26' enclosed car hauler. i know in actuality those are not bad numbers for the size of the truck, i still would like to know if i could increase my MPG. i am particular about my air pressures, i drive like a grandpa, run royal purple synthetic oil, i rarely drive wide open and rarely go 5mph over the posted speed limit. the only real mod i have made was replaced the stock intake with a voliant CAI with the snorkel. that has helped with throttle response and about .5 mpg on the fuel end of it. i know it is time to change the plugs/wires/fuel filter.

now my delema is this. where will i see the best bang for my buck? i am debating between replacing the exhaust manifolds and muffler (keeping the pipes) with a set of shorty headers and a specific muffler with the back pressure for towing (or am i thinking wrong here) and or getting a programer and changing some fuel settings in the computer. also what do you suggest or suggest to not waste my money on?

 

I have a 1999 1500 that gets 18 around town and ~10 towing a 20' cargo. My issue with doing upgrades for improved mileage is always the time it takes to get the money back, and how long I expect the truck to survive my abuse, lol
For example, an under drive pulley kit for the 5.3 is kind of expensive and the MPG increase is 1~2, an electric fan kit is around $400 ! another 1~2 mpg. So right there is around $800 for about 3 MPG increase overall.
With that example, using an increase of 3 MPG and a mean gas price of $3.25 you would save $721 in the first 20k miles. So if you drive 20k miles a year it would take a little over a year to recoup the investment in mileage before you are saving any money. If you plan on keeping the truck for a long time might be worth it, you be the judge.
This might seem a nerdy response, but in these tough times I count my pennies more now than before.
Later, Mark

 

that is a very good response. many people dont put paper to pen much and see how long it would take to pay off the differance. myself, i put on about 20k miles too going to work and towing a trailer every week to race tracks and dont plan on getting a new truck any time too soon.