So now you're at $2,000 for minimal improvement. Better keep it a long time. It'll take forever to break even.

When I posted this I expected to have people telling me to chip it. And not one guy did. Think I might change the plugs and then sock money for a 5.9 diesel. And buy some ear plugs for when I pull the camper.

Thanks for all the help guys!

I tow a trailer for work that weighs 3500-4000lbs with my 06 5.7 2wd with 3.92 gears. It is very flat around here, but I usually average 13 mpg while towing. I don't use tow haul and tow in OD on the freeway. There seems to be plenty of power.

do the normal sugested maintance. make sure your oil is in good condition. change it if necessary. get the tire pressure right. both on your truck and trailer. check the bearings and alignment of the trailer. check your air filter. replace if needed. it seems so elementary and people often look over it but all that stuff together can really rob power and effeciency. as for the 5.9, think about it this way. do you NEED the power to rip a house down? it should cost close to the same in fuel, the cummins might even be slightly better and yyou will tow a trailer much easier, but theres also alot more attention to the truck than a gas engine. but hey its a cummins. you could probably throw that engine off a cliff and it will start right up.