You'll get as many answers as you get responses to this post. Synthetic has more resistance to thermal breakdown, leaves far less deposits, will keep clean/clean a motor, has greater lubricity - less wear, is more stabel and can be run for much longer intervals. Do some reading at BITOG ( http://theoildrop.server101.com/foru...eads.php?Cat=0
) and you'll find answers to questions you never knew you had. As far as what you should use, totally up to you. I use Mobil 1 5w-30 with a Motorcraft FL820s filter, and change every 5000 miles.