Currently I run AMS Oil 10w30 in my Tracker.   I just like it because it got most of the highest ratings compared to other oils, Mobil 1 came 2nd most of the time.   I baby my Tracker.   Theres one thing though.   With synthetic, I have heard it many times on many of these mechanic radio shows me and my dad listen to, you dont want to switch to synthetic after around 40K miles.   I did it at 35K.   After that it is not supposed to have any real benefit to your engine and you just waste money.   Before that, it can help your engine run longer.   If your over 40 K (Im guessing most likely), I wouldnt do it.

I use Wal-Mart full synthetic in my '91 with 163K miles because I put a lot of miles on it due to a long (84 mile) round trip commute to work. I changed the oil every 3K when I was running conventional oil, but upped it to 5K when i went to synthetic. In addition, I also uses a larger filter (Wal-Mart ST3400<?>) that also fits a 2000 Taurus V-6 3.0. It provides more filter media and fits perfectly. I've not noticed any increase in oil consumption, but it's always burned a little (maybe 1 qt every 2500 or so).  I've asked about the difference between Wal-Mart brand and M1, and the consensus was that M1 has a better additive package, but with a 5K OCI it doesn't really make a lot of difference.  After running WM synthetic for over 10K miles I'm very happy and will continue to use WM oil and filters.  At $12.xx for a 5 qt jug and another $2.50 or so for the filter I thinks it's a great value.