There is nothing you can really do to get better gas mileage. The best way to keep your truck consistantly getting good mpg is to do regular maintenance. Like it was said before check your tire pressure, change your oil, clean/replace air filters, get a transmission flush at about 60k and 95k right before you get to 100k. Chevy/GMC trucks have a tendency to need a new tranmission at about 100k. Don't waste the money on the hypertech, it is a piece of sh** that only decreases your gas mileage and makes your truck shift really hard by putting a load on your tranny. Save the money and put it into general maintenance or get a diesel and run a Biodiesel fuel.

 

the best and only really effective thing is a mailorder tune

 

Theres plenty you can do to get better mileage...After headers, cai, and tune I gained 3mpg, then after the cam and retune I gained another 2mpg. After the 4.10 I'm thinkin maybe another 1mpg. I think some of the mail order guys can actually do a "gas mileage" tune.

 

ask DozerDan what his gas mileage was stock what it was like with a cam and Speed Density tune..i put a EFI Live Custom Operating System in his truck and tuned it Speed Density with no MAF or o2's and commanded his A/F to run at 15.5 at cruise..i think he said his stock was 17-18 and now hes at 21.5-22 mph and thats with a cam

 

i dont see how another tune can get much better gas mileage since the o2's still trim 14.7 a/f

 

A decent size cam too...

 

I don't see how a lower gear really helped overall fuel economy. If you're looking to tow a semi-large boat and retain good fuel economy, look for a diesel. It costs more up front, but overall, you just can't beat a deisel for hauling a load and it will likely get 20+ outta the gate, including in town driving, if you aren't a pedal freak. Besides, adding a 5,500+ lb load on a trailer will ruin gas engine economy no matter what you do to help(short of a bigblock, which will suck at all times). With a diesel, it will still hurt economy, but the difference isn't nearly as much as with gasoline. I've towed 9' tall box trailers with gas engines only to see 9mpg. The same trailers with diesel power doing the work averaged 15mpg. It was height, not weight which caused the difference in my case. A 34' boat can't be really low to the ground though, while on a trailer. Just something to think about.

 

Alot of guys on here with 20's or bigger that have gone with 4.10's claim better mileage simply because the motor doesn't have to lug as much

 

my dads been running a 2004 Silverado 4x4 4.8 for the last 3 years, and he loves it. Hauling a 5000 lbs dump trailer he gets about 18 mpg highway, without the trailer he said he saw it high as 21 mpg highway, he does about 80% city driving and gets around 19-20 average. Not bad for a 4x4 ECSB

 

My (truck in sig) best is 21.1 mpg at 70 on cruise (rpm is just under 2,000).