Answers to
that question are all over the board. I don't think you can go wrong either way.
Personally, I change oil @ 4-5K increments w/non-syn. This removes any contaminants (water, debris) and renews the oil additives. It's also less expensive (although syn prices have dropped in recent years) so conventional oil works for me.
230K on 5W-30 in my 99' and not a single issue requiring
any internal engine work to date, and she runs like a dream.
