When you cook spaghetti, do you add olive oil to the boiling water?
Yes, it is true that we don't add oil to the boiling water. I'm not aware of any good reason to waste extra-virgin olive oil that way! Some oil is always added at the end, over the sauce, when the pasta is already in the plate! It has to be raw, so that it retains its fruit nuances and texture.

If you are doing cold pasta salad and want to avoid sticky pasta, adding oil in advance won't help. You have instead to wash pasta under cold water to wash the starch away (you can put the pasta in the colander directly under the running cold tap).