Mpg question
 

Got a buddy that has a 06 megacab with a 5.9 auto totaly stock i he says he can put a double dose of cetane booster and drive it easy and only get 14 what could i do to it to make it get better fuel milage he doesnt care whether it adds power just wants more efficiency i know a 12 valve in and out but never done more than a clutch on this model help would be great

He needs an EFILive tune. He could put a single tune on it and if he likes that, add a CSP5 tune and call it good.

what is a csp5 tune

It's a calibration file that you load onto the ECM that let's you have 5 different tunes to choose from via either the EFILive device or a switch mounted in the dash. You can have up to six tunes on the 06-07 5.9's but I would think 5 would be enough.

Extra cetane will NOT help mileage.
Just like using more octane in a gas motor does nothing to help mileage and could do just the opposite.

Cetane and octane refer to the ability to light off.
On a gas motor, really high octane does slow the burn too. Do you want the gas to burn slow or to ignite at a controlled rate, and push on the piston while it is still at the top of the stroke? It does little if it is burning while the piston is down 1/2 way.
The energy is best used at the top of the stroke.

any programmer will raise milage efi smarty banks to name a few!

If he wants simple just get like edge e-z. Bumps mileage and power a bit. If he want adjustability I would go with the efi csp-5. That's what I'm getting for the wife's 06. Nice thing bout efi you have a lot more tuning options for his truck.