changing your oil at the proper interval is the most important thing....
go to an autoparts store grab 1 of every brand of oil each one will have an api service rating on the back.... the last time I used oil that came in a quart bottle and not out of an overhead dispenser the service rating was SL..... if they all meet the same service rating, why pay more?
will running synthetic in your daily driver help much doubtfull, if your already keeping the oil changed at the regular scheduled intervals. will it maybe give you that extra .001 hp that gives you that extra .0001 at the track is it worth 5-10 bucks a quart for that in my opinion no.
its all in how well you take care of what your driving my 94 plymouth minivan has 390,000 miles on it. never had anything but regular old 10w30 every 3000