What Oil Is Not Good for Frying and Why You Should Avoid It

Not every cooking oil works well for frying, especially when you’re turning up the heat. Oils like soybean, corn, canola, and sunflower just don’t hold up—they tend to break down fast and can release some nasty stuff when you get them hot.

Their unstable fats make frying a bad idea, which can mess with both the taste and your health.

If you want to fry food safely, skip oils with low smoke points or those packed with polyunsaturated fats. The wrong oil not only changes the flavor but can also create unhealthy byproducts.

Knowing which oils to avoid really helps you cook better and take care of yourself in the kitchen.

For more details, check oils to avoid when frying like soybean and corn oil.

Unsuitable Oils for Frying

Some oils just can’t handle high heat—they break down or create harmful stuff when you crank up the temperature.

Other oils burn easily or go rancid, which makes them unsafe for frying. It’s worth knowing which ones to skip so you don’t ruin your food.

Low Smoke Point Oils

Oils with low smoke points start to smoke and burn at lower temperatures. When you see that smoke, you’re also getting harmful chemicals and off flavors.

Take unrefined extra virgin olive oil and flaxseed oil, for example. Their smoke points usually sit below 375°F (190°C).

These oils work better for salad dressings or gentle cooking, not frying.

If you use oils with low smoke points, your food might taste bitter and the smoke can sting your eyes or even your lungs.

Go for oils with a smoke point above 400°F (204°C) for frying to keep things safe and tasty.

Unrefined and Cold-Pressed Oils

Unrefined oils and cold-pressed varieties have more natural compounds. Those bits add flavor, but they also burn fast when you fry.

Cold-pressed coconut, olive, and sesame oils just don’t hold up under high heat. Their delicate molecules break down quickly, which can leave bad smells or even toxic stuff in your kitchen.

These oils shine when you drizzle them or use them in dressings, or for low-heat cooking. If you really want to fry, pick the refined versions—they can handle the heat way better.

Oils Prone to Oxidation

Polyunsaturated oils like soybean, corn, and sunflower oxidize easily. When you heat them over and over, they form free radicals and other unhealthy compounds.

Restaurants often reuse these oils, which only makes things worse. Oxidation messes up the oil and can ruin both the flavor and your health.

Try not to fry with oils high in polyunsaturated fats, especially if you’re thinking about reusing them. Oils with more monounsaturated or saturated fats just do better for frying.

For more info on oil choices and frying, check out this discussion on oils for deep frying.

Health and Flavor Concerns

When you pick an oil for frying, you’ve got to think about your health and the taste of your food. Some oils make harmful compounds when they get hot, and others just mess with the flavor.

Both can ruin your meal or even your day.

Trans Fat Content

Trans fats pop up when certain oils get really hot, especially if they’re partially hydrogenated or super processed. These fats raise your risk for heart disease by bumping up bad cholesterol (LDL) and lowering the good kind (HDL).

You’ll want to avoid oils loaded with trans fats or those that easily make them during frying. Cheap vegetable oils like soybean, corn, and canola sometimes have trans fats or make them if you keep reusing the oil.

Look for oils labeled non-hydrogenated or ones with more stable fats, like olive or avocado oil. They’re just better for your heart and less likely to make those harmful fats.

Off-Flavors and Aroma Changes

When you heat certain oils past their smoke point, they start to develop off-flavors or strange smells. The oil breaks down at this temperature, and suddenly your food tastes burnt or just… off.

Flaxseed and walnut oil, for example, have pretty low smoke points. I wouldn’t use them for frying—just keep them for cold dishes or salad dressings.

If you want something that stays neutral, refined avocado or peanut oil can handle higher heat without messing with the flavor.

Every time you reheat oil, you bump up the chances of getting those weird, bitter notes. Oils like sunflower or grapeseed oxidize quickly, so it’s better not to reuse them. Otherwise, your food might end up tasting bitter or even a bit chemical.

Honestly, picking the right oil makes a huge difference. It helps you keep the flavors you want and steers clear of any nasty aromas. If you’re curious about which oils work best (or worst) for frying, check out this best/worst oil for deep frying thread.