I only tow the TT in my sig 3-5 thousand miles per year. I switched to synthetic fluid and saw no difference. Next oil change I am going back to dino. Dino fluids have come a long way even in the last 10-15 years. Unless you tow the majority of the time or see temps above 200 on a reg basis I don't believe there is much if any benefit to using the synthetic, except it will make your wallet lighter. On the filters, I would change both of them. I don't care what Ford says, you should drop your pan anyway to look for debri and clean the bottom of the pan, so why not change the filter?