You want the downs first?
>It costs more.
>The engine will leak a little, I had this problem with synthetics all the time. Started using Mobil 1 in 1977 on and off and used it all the time in my Turbo powered car.
Plus side:
>It has a higher coking temp. takes longer to break down under pressure.
>flows better when cold - more protection on startup
>generates less dirt in the engine - no ash.
>since it is cleaner many run it longer between changes.
