Although too much oil is bad for you, you do need some oil in your diet. Some nutrients and vitamins need oil to work properly in your body.
A 1/2 serving of light mayonnaise is not going to hurt your diet. Using enough olive oil so that meats like fish, chicken, and beef will not stick to the pan (1 teaspoon) is not going to wreck your calorie count either.
I know a lot of people like using the spray oils but using olive oil is actually quiet healthy in moderation and it tastes better.