Pot lid on or off when boiling pasta, please!

what does everyone else do! I always leave the lid half on but it sometimes boils over and then there''s cleaning up to do.

off

off or it will boil over

Off.and apparently it is a kitchen myth that adding oil to the water will stop it sticking together.Best to add the oil after you've drained it.

http://kitchen-myths.com/

the teaspoon of oil is to prevent a boil over - with the lid off

The oil is to prevent sticking, the salt is to make the water boil more quickly and the lid off is to stop the water boiling over

As has already been noted oil helps to prevent boiling over. The reason for this is that the foaming action in boiling pasta is caused mostly by proteins that break free from the pasta, and the oil creates gap between these proteins.
More substantially, it's just not true that, "Oil in pasta water just floats on top." Modern science has done a lot to challenge the long held idea that "water and oil don't mix." The two biggest challenges to this idea have been based on temperature, and aqueous gas. Experimentation has proven that water devoid of aqueous gases will mix with oil, and it is generally assumed that this means that the less dissolved gas in the water, the more it will mix with oil. As any devoted tea drinker knows, the boiling of water very rapidly depletes the dissolved gases contained therein. With the exception of very quick cooking pastas, like angel hair, the amount of time the water will boil during the course of cooking your pasta will diminish the dissolved gases in the water to the extent that it will mix with the oil to a certain extent. While it would take a very long boiling time to achieve a complete colloid, it's quite obvious, if you add oil to your water, that the two cease to be fully separate after just a couple minutes of boiling. Scientists have long observed that high temperature water mixes better with oil than does low temperature water, though, in light of recent evidence, this may not be a factor of temperature, as long assumed, but of percentage of aqueous gas.
Either way, none of this changes the fact that adding oil to the water isn't going to stop your pasta from sticking to itself, and that, if you're cooking your pasta right, you shouldn't be having this issue anyway.
Adding plenty of salt means your water will boil at a higher temperature - \which is beneficial.

My pasta never sticks, I never use oil although was told this was why you should - I buy Italian-made pasta as the cheap stuff always sticks and tastes gross

better still - make your own

I would if I could be bothered but I can't so I don't - pasta maker has never been out of the box it came in about 10 years ago.