Vegetable oils tend to "polymerize", that is become sticky and solid. Castor oil, for instance, is an excellent lubricant that was favored for racing autos and motorcycles for a long time. The reason it never became popular for regular cars was that it also built up a lot of sticky, cruddy goo. Racing engines are regularly torn down and rebuilt; no matter. Not so your sedan. The oils used in oil-based paints are usually vegetable-based as well; they tend to become quite solid after a while.
As I've noted before, lubes, especially chain lubes, seem to be a "thing" for serious cyclists. Chain lube threads on dedicated bike forums tend to go on and on and on... It's the engineering mentality at work. "Maybe I can get 100 more miles out of my chain if I concoct my own special blend!" Maybe... Chain lubes are cheap. They cost at most what, 10 bucks for a bottle sufficient for a year? As well, chains are cheap. Oh, you can spend a lot for super-deluxe items, but a good, well-made standard chain is under 20 bucks and will last most riders as long as they keep the bike if lubed and cleaned properly.
Related
- "Best chain lubricant for road bikes?""Best chain lubricant for road bikes?" Asks about the best lubricant out of conventional oils and lubricants
- "Substitutes for chain lubricants""Substitutes for chain lubricants" Asks about non-traditional substitutes for chain lubricant