Oil in the cooking water prevents sticking. That advice is found in dozens of cookbooks. It has the opposite effect.

Oil and water do not mix. The oil floats on the water and largely disappears when draining. The small amount that remains makes the pasta's surface smoother. And a smooth surface holds sauce less well.

You prevent sticking by mixing the pasta with sauce immediately after draining. And by eating it right away.

More about the chemistry of pasta in the latest Koken met Kennis.