Adding a splash of oil to the pot is one of those kitchen habits that sounds sensible, but in practice does almost nothing for preventing pasta from sticking. Water and oil do not mix, so the oil rises to the surface and sits there as a separate layer. Your noodles are boiling underneath, in contact with hot water, not being bathed in oil.
That is the simple physics behind it: surface tension and density keep the oil floating on top, while the pasta moves through the water below. By the time you drain the pot, most of that oil never touched the noodles in a meaningful way. The only thing it really changes is the surface of the water, and that does not solve the real cause of sticking.
What actually makes pasta cling together is starch. As the noodles cook, they release starch into the water, and if they are crowded or left sitting without movement, that starchy coating acts like glue. The best defense is not oil, but enough water, a pot large enough for free movement, and a quick stir right after the pasta goes in and again during the first couple of minutes.
What to do instead
- Use plenty of boiling water so the pasta has room to move.
- Stir immediately after adding the pasta, then once or twice more early in cooking.
- Keep the water at a steady boil, not a weak simmer.
- Drain as soon as the pasta is done, especially if you are not saucing it right away.
If you want noodles to stay separate after draining, the real fix is sauce, not oil in the pot. A well-emulsified sauce clings to pasta far better than a greasy slick ever will. If you are making a pasta salad or need to stop cooking fast, a brief rinse can help, but for hot pasta dishes it usually washes away flavor and starch that help the sauce adhere.
So yes, oil in the water is mostly a myth. It may make you feel like you have done something, but it does not meaningfully protect the pasta. If you want reliably non-sticky noodles, use enough water, stir early, and treat the pasta properly after draining. That is the old-fashioned method because it actually works.
Try it with this recipe: https://en.alwaysyummy.recipes/classic-spaghetti-aglio-e-olio-garlic-olive-oil-and-chili-in-15-minutes/