1986 XJ6 oil leak partially cured

Several years ago I had the valve cover gaskets and the front crankshaft oil seal replaced on this 1986 XJ6 car, which I’ve owned for more than 23 years now. After these items were replaced, both leaks improved significantly, but whenever I’d wipe the back of the valve cover gasket after a good run with a clean paper towel there would always be a slight oil moisture ‘residue’ on the towel. As for the front oil seal, though the situation was much improved, I’d still always find a drop or two on the ground under the front of the oil pan after the car was left to sit for a few hours or days. Last week, when going through the garage, I found a bottle of an item I hadn’t used for some time, the product known as ‘Marvel Mystery Oil.’
I remembered the product was known for cleaning fuel systems as well as making engines run a bit quieter (not that my engine is noisier than it should be.) So I added 8 ounces to the crankcase as well as four ounces to each gas tank (both of which were close to full), just to see what might happen, if anything. Here’s the interesting part: I’ve driven the car twice since then, covering about 50 miles. When I parked the car in the garage after yesterday’s drive, I performed my usual ritual of wiping the back of the exhaust side valve cover at the gasket. To my surprise, the towel came up clean and dry. I removed the oil dipstick, fearing perhaps the towel was dry if the car had run out of oil! No, oil level on the dipstick was right where it should be. Next, I crawled under the car to place the customary aluminum (or aluminium for listers located in right hand drive locations) pan under the front of the oil pan, and found only a drop or two on the pan, much less than usual.
So, I’m wondering, besides quieting sticking lifters and removing sludge and cleaning injectors, is it possible a byproduct of Marvel Mystery Oil might be a softening and expanding of seals as well? I’m very curious…
Thanks for reading…
Mel R.