C6 oil confusion. I have heard so much contraversy over fluids. Personally I think type F and Mercon both work well. I fell most failure is due to heat rather then fluid type. This is assuming a proper rebuild. I dont recomend using the Mobil 1 oil simply because its damn expensive to buy 13-14 quarts of it! Ford started using the Mercon in the C6 around 1977. I would recomend choosing a fluid based on the year of your car. This avoids confusion in my opinion. Use types F in the pre 1977 cars and Mercon in 1977 and later. I hope this helps.