As someone who is allergic to most kinds of cooking oil, I do not use any, just stir the pasta in the water while it is cooking every minute or so, and then the pasta goes from the strainer directly into the sauce afterwards - so there's no chance for it to stick.

If I were cooking the pasta for later use, so it needed to sit for a while once cooked, I'd toss it in a bit of butter to keep it from sticking together.