My check engine light has been on since June or so and I found out it was my EGR valve. I hear this can affect my emissions (duh) but also fuel economy. I have noticed a drop in my fuel economy. I barely get over 300 miles on about 10 gallons. I used to get close to 400 every tank. I will be buying a new one soon before December cause thats when the registration expires. Is this the reason why im getting poor mileage or is it something else.