Dunno, it's about twice the price but it lasts twice as long, so it all works out, right? Also I understand you can push it further if you have to with synthetic.
I just don't know if it'd be worth it for an older vehicle that has used the regular stuff for so long. But otherwise...even though it's pricier, it might well be worth it!
I think if you are going to push it longer, it is much better to have a synthetic. Pennzoil turns to a thick sludge when it is old. Ramius lost an engine in a newer truck because of it. He rarely drove it, so it sat longer than the recommended time, but not the mileage. His engine seized and was ruined. The oil that came out of it looked like gloppy jam. The synthetics don't do that. No more Pennzoil.