Cooking oils and fats react differently to heat, but in general, the hotter they get, the more they break down and eventually start to smoke.
(Scroll down to see the comparison table of the smoke points of different oils and fats.)
That means that certain oils are better for high heat cooking, like sautéeing or deep-frying, than others. The temperature at which a given oil will start to smoke is called its smoke point.
To say that an oil has a high smoke point means that it can be heated to a relatively high temperature before it starts to smoke.
Why is this important? For one thing, if you cook with oil that's heated past its smoke point, it will impart a burnt flavor to your food. But also, heating your oil too far beyond its smoke point could possibly start a fire. So it's a good idea to know how hot your oil can go so you're always using the right oil for the job.
Vegetable Oils Have Highest Smoke Points
As a rule, vegetable-based oils have higher smoke points than animal-based fats like butter or lard. The main exceptions are hydrogenated vegetable shortening, which has a lower smoke point than butter, and olive oil, which has a smoke point about equal to that of lard.
Refined Oils and Light Colored Oils
Another factor is the degree of refinement of a given oil. The more refined an oil, the higher the smoke point.
That's because refining removes the impurities that can cause the oil to smoke. A simple rule of thumb is that the lighter the color of the oil, the higher its smoke point.
Finally, it's important to note that any given oil's smoke point does not remain constant over time. The longer you expose an oil to heat, the lower its smoke point becomes.
Also, when you're deep-frying food, little bits of batter or breading will drop off into the oil, and these particles accelerate the oil's breakdown, lowering its smoke point even more. So in general, fresher oil will have a higher smoke point than oil you've been cooking with for a while.
Below is a table that shows the smoke points for several of the most common cooking fats and oils. In some cases, you'll see a range of temperatures rather than a single smoke point, because of different degrees of refinement among numerous brands of oils as well as other variations.
Smoke Points of Fats and Oils
|Vegetable Shortening (Hydrogenated)||325°F|
|Olive Oil||325°F - 375°F|
|Corn Oil||400°F - 450°F|
|Grapeseed Oil||420°F - 428°F|
|Canola Oil||425°F - 475°F|
|Clarified Butter||450°F - 475°F|
|Sunflower Oil||450°F - 475°F|
|Soybean Oil||450°F - 475°F|
|Safflower Oil||475°F - 500°F|