I heard that there was a new fluid system on the exhaust for the 2010 emissions laws that instead of dumping fuel in the system if dumps this stuff in to burn off the stuff in the exhaust system may be thats what the square thing is on the bed

 

Your talking about urea.

Hears a good article about urea. Disregard the AdBlue name as that is just a brand name.

AdBlue – Diesel Emissions Fluid – ADBLUE Clean Diesel Urea Solution

 

It is not instead, it is in addition too. The DPF captures soot, this needs extremely high temperature to burn the soot off, which still requires a lot of fuel. Urea injection reacts in a special catalyst to reduce NOx emissions, and thats it.

Current engines can get by with a NOx absorber and lots of EGR. EGR really hurts combustion effeciency on Diesels. So the urea injection will give you a slight mileage gain in the fact that you can use less EGR. But it will still never be as good as the older pre 07 egines because you still need to burn off the soot in the DPF.