Selecting a cooking oil used to be a case of "[vegetable oil], [olive oil] or [butter]?". No longer. These days it is easy to find all kinds of fancy oils. This is a [mixed blessing] — it allows far more flexibility, but makes selecting the best oil for the task a lot harder.

Ultimately, the original three are enough to provide an adequate solution for any kind of cooking. But then, [jeans], a [t-shirt] and a [suit] provide an adequate solution to clothing. Having access to a few extra oils is a great way of adding a little more variety to food. On the other hand, it's not worth going out and buying a bottle of every kind of oil for home use — there's considerable overlap in styles, and oil doesn't keep forever.

A note on terminology: strictly speaking, an [oil] is [liquid] at [room temperature] whereas a [fat] is [solid]. The distinction is often ignored when cooking — butter in particular will melt with very little heat, so is often used as a cooking 'oil'.

Oil Characteristics

Oils can be classified by two characteristics: [flavour] and [smoke point]. For a few oils, [stickiness] and [reactivity] can also be relevant issues. Finally, some oils are sold with added flavourings.

Flavour

Oils with a strong flavour can significantly alter the taste of the food. Sometimes this is desirable — the distinctive taste of [sesame oil] is an important part of many [oriental recipes]. Sometimes, though, strong oils can ruin a meal. When working with delicate fish in particular, the wrong oil can kill the meal's flavour.

Although not strictly speaking a cooking issue, flavour makes even more of a difference when mixing a [salad dressing]. Here the oil usually forms a significant part of the end flavour, so selecting the correct oil is critical.

Smoke Point

When an oil is heated above a certain temperature, it will start to decompose. The temperature at which this happens is called the [smoke point], because most cooking oils will give off nasty smoke when they break up. The smoke point is lower than the [flash point], which is where the oil catches fire. None the less, it is extremely important never to exceed the smoke point of an oil. As well as a nasty taste and smell, the smoke from some oils contains various [carcinogenic] compounds.

For low temperature cooking, the smoke point is largely irrelevant. When frying or oven cooking at higher temperatures it is sometimes a significant issue, and when making a [sauté] or [stir fry] it should be a primary concern.

Other Considerations

A few oils are not particularly good at preventing food from sticking to the pan. This can be a problem if food is being fried for more than a few minutes.

Most oils are fairly inert and will not react with food or pans. A few obscure oils have been known to go badly with certain foods and pan surfaces, however — when selecting an uncommon oil, it may be wise to check whether it reacts with anything.

Some oils claim to have various health benefits. Separating the genuine differences from the [kooky pseudo-science] is rather tricky — chances are, the only way that this is at all relevant is that certain otherwise obscure oils can easily be found in [health food store|health food stores].

Flavoured Oils

Recently, certain producers have started making oils which come pre-flavoured — popular choices are [garlic], [lemon], [chilli], [ginger], [basil] and [rosemary]. This is a slightly controversial topic. Personally, I prefer to add flavourings when cooking; others find pre-flavoured oil more convenient. Some things to bear in mind:

The smoke point of pre-flavoured oils will be lower than that of the clean equivalent.
Pre-flavoured oils will not last as long before they start to go nasty.
Some people are concerned about [Flavored oil and botulism|botulism] when using flavoured oils. This may be an issue for home made oils, although its significance is debatable, but pre-made oils should contain lots of [nasty additives] to eliminate any risk. There are [salmonella|plenty] [carving knife|of] [poisonous mushrooms|ways] [how to set yourself on fire|of] [Campylobacter jejuni|making] [bacillus cereus|yourself] [escherichia coli|ill] when cooking, most of them far more common than [botulism].

Popular Cooking Oils

Now for some of the more popular cooking oils. Note that the smoke points will vary considerably depending upon whether the oil has been [refined]. There are various [tables of smoke points] around, all of which are only very rough approximations and many of which are misleading on the issue of refined oils.

[Sunflower oil], [Vegetable oil], [Rapeseed oil], [Canola oil]: Fairly little taste. Fairly low smoke point.
[Butter]: Slight taste, usually not noticeable in the end product. Very low smoke point.
[Olive oil]: Moderate to strong flavour depending upon the style. Medium smoke point.
[Sesame oil]: Very strong flavour, plays an important part in certain Japanese and Chinese recipes. Medium smoke point. Do not use this oil in salad dressings — it will drown out the flavour of the other ingredients.
[Grapeseed oil]: Very mild flavour, very high smoke point. It remains slippery for longer than most other oils. Ideal for [sauté|sautés], making crunchy [jacket potatoes] and high temperature oven cooking.
[Peanut oil]: Noticeable flavour, high smoke point. Often used in salad dressings.
[Walnut oil]: Noticeable flavour, fairly low smoke point. Better for salad dressings than for cooking.
[Avocado oil]: Noticeable flavour, but not overpowering. Extremely high smoke point. Very viscous — less of this oil is needed when cooking.
[Bacon grease]: It is rumoured that [deep south|some people] actually use this stuff for cooking. It has a baconish flavour, a very low smoke point and is prone to catching fire. Other variations on this theme include [lard], [dripping] and [ghee] — these are all fats and aren't particularly good for frying.

If I could only have a single oil, I would go with [grapeseed oil|grapeseed]. It's not a conventional choice, but it's not very expensive and the high smoke point and low flavour make it fairly versatile. Others have different opinions — different oils suit different cooking styles. [Experimentation is encouraged].

cooking oil (thing)