Do you really believe an oil additive can fill the gaps between rings and cylinder walls? I certainly don't. If you look at Wynns website for this material its only specific claim is that it "Revitalizes rubber and neoprene seals of crankshaft, camshaft and valve stems." In other words it softens hard rubber to temporarily restore its ability to conform to metal surfaces. No other claim is specifically made, though much is implied by typical advertisers weasel words.
Don't be misled into thinking there is a magic cure for wear. Don't waste your money on the stuff. If your rings are worn your engine needs an overhaul, which years ago would mean a re-bore and over-size pistons. Nowadays it probably means a new engine.
However the diagnosis of worn rings may be pessimistic. I suggest you get a compression test done on the engine, which can help diagnose whether the bores or the valves are leaking. Getting valve leaks repaired is much cheaper than getting a re-bore.