Can anyone tell me how many gallons of propane to diesel is used with moderate highway speeds empty on a 6.0 2006 auto 4x4 with a propane injection system [Bully dog].  and how about dimensions on a 15 gal  under truck tank? thanks  

I have a auto duramax 06 4x4 with propane I use a ats system Your truck wont use any propane at highway speeds. all propane systems use a intake vacume diaphram which controls propane delivery. the propane system is turned on by a selanoid that is triggered by boost preasure usualy at 5-10 psi of boost. then once the selanoid is open you truck has to draw enough intake vacume to pull the diaphram down to open the main valve. I have a boost gauge and at highway speeds I rarely am over 5 psi of boost so the system is not even on. Even if your over 5 psi that doesnt mean your drawing enough vacume to open the main valve. you can put a lite spring to let the valve open. To answer your ? Ats says 1 gallon of propane per 60 miles. Thats only going to happen if your going 90mph loaded. You wont use much at all at highway speeds. I just drove 2400 miles az to ny and used only eight gallons that 1 gallon to 300 miles. If your considering propane for economy its not worth it they claim 10% better economy and you never get whats claimed. I your looking for power its awsome it just takes a couple mods of a stock propane kit to get them to get them working great. As to your tank ? I dont recomend an under truck tank but 15 Gals would last very long. I use a 8 gal fork lift bottle lasts at least 1500miles and is alumian unlike under truck tanks which are steel which rust internaly and clogs lines. Not to mention not to many propane places dont have a hose long enough to reach your truck the forklift bottle easly unclamps and is a good idea to remove for warrenty work. I no every one has there own opions on propane but I have first hand experance. NOT for economy but if power is what you want its a must have  

I HAVE TO DISSAGREE IM RUNNING PROPANE MYSELF AND I AM SEEING A MILAGE INCREASE. I HAVE A 19.0 GAL. TANK AND MY MILAGE INCREASED BY 5 MILES PER HOUR.    

In theory, you should see an increase in fuel economy with propane. Of course, if you're on the throttle all the time, then you might not.  

What about the Superchips PDI system..then it runs based off what the computer says, not a vacuum created.