...knows everything (apparently) about all things mechanical. He is a mechanical engineer who started playing with engines when he was 13. He was a bachelor until 42. His cars are his babies. He works with oiled gears and cranks under fairly heavy loads. Did some testing regarding synthetics vs traditional oils vs traditional oils with additives, shopping for best performance in crank cases under heavy loads. In a very reproducable, scientific manner he ran tests, searching for something to reduce his wear. He stumbled onto an obscure product that when added to 30 weight oil, outlifted even the synthetics nearly 10 fold. He was so blown away he now talks like he owns the company. Neither of us have any affiliation, I assure you. The product is made by Lubri-Loy, and is called Revive. If there are others that have ability to test, I'd love to see this confirmed, again and again. We're all convinced. Not many places sell it, it's expensive, and hard to find. It's also apparently miraculous. Good luck.
The only issue you might have is leaky seals that have dried out in the last 22 years. If there aren't any leaks, then regular petroleum oil will be fine. Oil additives are generally a sales gimmick.