Cooking oil is plant, animal, or synthetic fat. It is used in frying, baking, and other types of cooking. It is also used in for flavoring such as in salad dressings and bread dippings. Oils with a higher smoke point (see table) are better for cooking, while other others are more suitable as edible oils due to flavor or composition.
The proper way to dispose of cooking oil is to put it in a sealed, non-recyclable container and discard it with regular garbage. Placing the container of oil in the refrigerator to harden makes disposal easier and less messy. Do not dump cooking oil in in your drain.
Below are the most common cooking oils—there are many more. Also listed is the Smoke Point, Saturated Fat Acid (SFA), Monounsaturated Fatty Acid (MUFA), and Polyunsaturated Faty Acid (PUFA) percentages. Not all columns total 100%. Click the arrows in the column headers to sort.
You probably want to keep two kinds of oil around: one for sautéing and dips, and one for baking and deep frying. Extra Virgin Olive Oil is the healthiest oil for the first task, but remember it has its own flavor, and it has a "medium" Smoke Point of 190°C (374°F). Once you hit the smoke point, any oil will oxidize, the flavor will change for the worse, and it may possibly release free radicals that can have negative health effects. However, there is an ongoing debate about using Olive Oil at high temperature, and some research says that what you can get away with depends a lot on the quality of the product.
For other cooking tasks, Canola is a great all-around, low-cost oil that has reasonable types of fat, a high smoke point, and a neutral flavor. The only negative is that it is highly processed, so it doesn't have many nutrients.
Finally, when you see the term "Vegetable Oil", it is just a generic name for any oil made from vegetable matter, and it's possibly a blend of multiple oils. Read the label carefully to make sure you're getting a quality product rather than a low-quality, highly-processed surprise.
This topic is fairly complicated, and I'm still studying it. Specifically, I need to look at Avocado, Corn, Grapeseed, Peanut, Safflower, Soybean, Sunflower, and probably other oils. That's a lot of work. Coconut Oil sounds terribly unhealthy. MB.
References: Wikipedia Cooking Oil and other www sources.