if u oil seals are leaky, its gonna leak no matter what oil, unless u switch to a thicker grade (which is a band-aid fix).

new seals are like what $50 or less?

synthetic cost more. gives u that nice yellow tint inside your engine. but its worth it to me.

i have heard once u go synth, dont go back to conventional though. i forgot the exact reason.

i run mobil1 10w-30 in my 150k KA, with oil changes about 2900-3200 miles (yeah sue me im lazy). its usually still pretty gold and doenst smell overly burnt or broken down.