I recently replaced my EGR valve after my check engine light went on and of course I was getting crappy GM so you would think that after replacing it I would get better GM but I'm still getting 18 mpg! any suggestions on what it might be? i think its the fuel filter but then again..
Any help is appreciated.

 

It could be the winter fuel and the type of driving you do... I've gotten 18's before in the winter when I drive nothing but city.

 

do a tune up