The 4130 World Sport was a good bike, it did not have a cartridge bottom bracket, just the basic spindle/cup style which was common back then in all price ranges.

+1 Time for a basic bearing and grease replacement for the bottom bracket, and a good time to do the front and rear hubs as well. This is a simple job, lots of help on line, or take it to your favorite shop. This is good basic, somewhat routine (every couple of years) maintenance. And something that on older bikes in my experience hasn't been done in decades (if you bought the bike used).

+1 Bottom bracket and even hubs require some special tools, nothing huge, but something I would not do with just common homeowner type tools.

+1 Co-ops are great if there is one in your area.

+10 Forget about that pour oil down the seat tube idea. You need to clean (or even better, replace) the old bearings, new grease, adjust and go.

Eventually, if not maintained, you can do damage to the cups and cones (areas where the bearings ride), and that will cost you a lot more. Those parts, if maintained can last decades.