i run the amsoil at a 11,000 mile interval and pay $5 a qt at napa for it ( yes its the full synethitic good stuff they just sell so much a month that its cheap
I also run full amsoil in my power stroke and it takes 17 qt but i still think its weel worth it

1998 mercury Mystique 2.5L with that stupid slush box only engine mod so far a optimized tb dark blue with midnight blue leather interior finnaly got rid of the door ding guards and pinstripe