I drive a 1994 mazda protege 1.8 SOHC with 125k on the clock. As far as I know the car has never had synthetic oil in it. It has had 3-4k oil changes where ever was cheapest for its life. So upon acquiring this car i want to run MMO or something else to try to clean it a little and then run a good synthetic like Penzoil Platnium, Mobil-1, or preferably Castrol Edge. It has 2k on the GTX thats in it now. Should I add the MMO the last 100 or so miles before the change or should i just substitute it for a quart of syn on my next change. and whats a good filter thats pretty cheap. thanks for the info guys.