My saturn, 96 sc2 150k oil is getting blacker and blacker and I am using about 1 1/2 quarts between oil changes. I use to change oil every 3000 miles but have started moving it up to 2500 because of the color. I started with mobil one oil synthetic from about 75k miles but since about 125k have started using penzoil because of the cost of mobil one and the frequent changes. Is there anything I can do to safely clean this engine! I have also been producing a lot of carbon for I get the occassional egr code because of a stuck pintal or whatever it is called. I've been thinking about taking the car into a dealer tht decarbonizes engines but was hoping for a better remedy. Phil