Oil And Pan: A Bad Mix?

Mixing oils in a pan is generally considered a bad practice. This is because different oils have different smoke points, and heating a mixture of oils past the smoke point of the oil with the lower smoke point will result in both oils being wasted. Additionally, oil degrades significantly following prolonged oxidation or multiple heating cycles, and broken-down oil can contribute to sticking and residues on food. Furthermore, mixing hot oil and water in a pan can be dangerous as it may cause a fire.

Mixing different oils does not average out their smoke points

Mixing different oils with varying smoke points does not average out their smoke points. The lower-smoke-point oil will start to degrade and burn at a lower temperature, and heating the mixture past this point will waste both oils.

For example, when mixing olive oil and butter, the olive oil will start to degrade and burn at a lower temperature than the butter. This means that heating the mixture past the smoke point of the olive oil will waste both oils.

Similarly, when deep-frying bacon, the bacon fat released during cooking can lower the smoke point of the oil being used. This can result in the oil smoking and burning at a lower temperature than expected.

It's important to note that heating oils past their smoking point can lead to the formation of harmful compounds and an unpleasant burnt flavor. Therefore, it's best to choose an oil with a smoke point suitable for the cooking method being used.

Oil degrades after prolonged oxidation or multiple heating cycles

Oil degradation is a significant concern for those operating critical industrial equipment, such as car engines. It can impair the lubricating abilities of the oil, leading to costly failures. One of the main causes of oil degradation is oxidation, which occurs when oil molecules react with oxygen molecules. This process can result in an increase in viscosity and the formation of varnish, sludge, and sediment.

Oxidation is accelerated by temperature. For every increase of 18°F (10°C) in temperature, the life of the oil is halved. Therefore, keeping the oil as cool as possible when in use is crucial for preventing rapid oxidation and extending the life of the oil.

Oil can also degrade through thermal breakdown, which occurs when the oil comes into contact with hot surfaces or experiences a rapid increase in temperature due to the adiabatic compression of entrained air bubbles. This can lead to chemical changes in the oil, such as the formation of carbon and oxide insolubles, which darken the oil's colour.

Additionally, oil can undergo additive breakdown, where the additives in the oil, such as detergents, dispersants, and anti-wear agents, break down or become less effective over time, reducing the oil's ability to protect the engine.

In the context of cooking, oil degrades after prolonged oxidation, such as leaving it in contact with a hot surface for an extended period, or multiple heating cycles. A heating cycle refers to the oil being heated to a set temperature, dropping when cold food is added, and then heating up again. Tests on olive oil have shown that as few as eight heating cycles can reduce the flashpoint of the oil by more than 60°C. Therefore, it is important to avoid heating oil past its smoke point and to store oils in a cool, dry place to prevent oxidation and degradation.

Oil and water do not mix and can cause flare-ups

Oil and water do not mix, and this can cause flare-ups. This is because water molecules are polar, with one end carrying a slight negative charge and the other end carrying a slight positive charge. These charges allow water molecules to form hydrogen bonds and attach to other polar molecules, including other water molecules. Oil molecules, on the other hand, are non-polar and cannot form hydrogen bonds. When oil and water are put together, the molecules of each liquid bunch up together, forming two distinct layers.

The immiscibility of oil and water can lead to dangerous flare-ups when heated oil comes into contact with water in a pan. Water has a boiling point of 100°C, while oil can be heated to much higher temperatures, such as 180°C for frying. When hot oil and water come into contact, the water will rapidly boil and try to escape as steam. This steam can carry tiny droplets of oil with it, creating a cloud of oil mist. When this oil mist comes into contact with an open flame, such as a gas stove, it can ignite and cause a fire.

To avoid flare-ups, it is important to ensure that your pan is completely dry before adding oil. If you are using a non-stick pan, it is also recommended to heat the pan first and then add the oil, as heating the oil in the pan can cause it to break down and become gummy, leading to sticking and residue on your food.

While oil and water do not naturally mix, it is possible to create an emulsion by vigorously shaking or mixing them together. However, this emulsion is unstable and will separate over time. To create a stable emulsion, an emulsifier such as mustard or mayonnaise is needed. Emulsifiers have a hydrophobic (non-polar) end and a hydrophilic end, allowing them to surround oil droplets and help them mix with water molecules.

Oil left on a pan can form a sticky layer that is hard to clean

To prevent this from happening, it is important to heat the pan first and then add the oil or butter. This way, the oil spends less time in contact with the hot surface and is less likely to break down. It is also important to use the right amount of oil when cooking, as too much oil can cause it to become sticky and difficult to clean.

If you do end up with sticky oil residue on your pan, there are a few effective ways to remove it. One method is to use vinegar and salt or baking soda. Fill the pan with white vinegar and let it sit for at least half an hour. Then, add a little salt or baking soda and scrub the pan with a sponge or brush. Rinse the pan thoroughly with water. Another method is to fill the sink or a large basin with hot water and add a few drops of dish soap. Submerge the pan in the soapy water and let it soak for 15 to 20 minutes. The hot water and soap will help loosen the oil, making it easier to remove.

It is safe to mix different brands of oil in a car

Mixing different types of cooking oils can be a bad idea. The oil with the lower smoke point will start to degrade and burn at a lower temperature, meaning that mixing oils and heating the mixture past the smoke point of the lower oil wastes both amounts of oil.

Mixing different brands of motor oil in a car, however, is perfectly safe. As long as the oils are the same weight and have the same specifications, such as API and SN ratings, they will be compatible. Mixing brands of oil is better than letting oil levels get too low, and it is common for people to switch oil brands between oil changes, so there is always some oil left in the engine from the previous brand.

It is worth noting that some people do advise against mixing different brands of motor oil, as different brands may have different additives, and it is not known how these would react together. However, the general consensus is that it is safe to do so.

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