First off, let me point out that I would never pour synthetic oil in my stovebolt - my truck leaks oil, it burns oil, it has no filter.
30 years ago my dad started putting synthetic amzoil in his vehicles. It cost 4 times more than regular oil, but he ran it 4 times longer. I believe he went sometimes 20 - 25,000 miles without changing oil, although he changed the filter and added a quart more often. All through the 70's and 80's he never had a vehicles that didn't last over 200,000 miles.
I believe synthetic oil can be a good product if it is used sensibly. But I also believe it has no place in an engine from the 50's.
