Personally I would stick with non syn you can get something like
Trop-Artic for 1.47/qt that has 95% of the benefits of syn for way cheaper..
It is a group III oil (like castrol syntec) another good choice is the motorcraft oil
its also a group III oil. If you want syn I wouldnt bother with castrol syntec as its
sorta a "Fake" syn oil. I'd go with something like M1 or Pennzoil Platinum.
Currently I have 12 more qts of Pennzoil I scored for 1.89 after rebate.
Then I have 16 qts of Valvoline Maxlife Syn that I got for Free just had to pay tax
then full rebate.
Syn wont hurt anything though the worst it could do is clean out some deposits
and cause a slow leak.. It isnt actually causing the seal to leak but by cleaning it a leak may develop that was plugged by crap from regular oil.
If I may suggest anyone who wants to know more about oil that you could
possibly want to know.. visit bobistheoilguy.com
their forum link. There is more info that you would believe
about oil filters and different oils. Just make sure to be polite if you post
because it is VERY moderated and FAMILY orientated