“Oil stops pasta from sticking.”
Half true. In most cases it will effect the water more than the pasta.
Adding a little dose of oil does not prevent the pasta from sticking, but it can stop the water from foaming or boiling over. However, this can also be achieved by making sure you use a large pot and also by reducing the heat a little (but still maintaining a boil).
Adding a substantial dose of oil to the pasta water can prevent sticking to some extent, but at a great price. Pasta that’s cooked in oily water will become oily itself; sauce does not stick to oily pasta, which does not absorb the sauce and is left mostly flavourless.
See other: Mythconceptions?