[mwebb]

Originally Posted by Christ

Well, not exactly tongue in cheek, but I did know that it wasn't correct.

EGR recirculates exhaust gas back into the combustion chamber to lower combustion temps so that Nitrogen doesn't combine with other compounds to form NOx, as I understand it.

Of course, if there is unburned fuel in the exhaust, part of it will go back through the EGR system. Not 100% about it, but I believe that to be the reason for sludge/yuck buildup in the EGR passages (unburnt or partially combusted fuel mixture).

I posted it like that because I was waiting for a response, as I frankly don't think he has any idea what it does, either. I was just trying to verify by leading. Lawyers do it all the time!

========================
your answer was more correct than "his" ...
but
yes over time carbon and doo doo build up in and around EGR passages on some systems --- may be some partialy burned fuel and some
residue from engine oil deposits from
low quality oil use -
................................
EGR does dilute combustion gases with INert gases
so;

combustion temperatures are reduced .
thus reducing NOX

and

EGR can improve fuel economy by reducing suction throttleing loss

because
EGR
effectively
reduces the size / displacement of the engine during the time EGR is active / operating

so
the operator needs to apply more throttle opening for the same amount of power to the wheel s when the EGR is active