How to make olive oil last longer in Spain without making this common kitchen mistake

With olive oil still treated like liquid gold in many kitchens in Spain, more households are saving used oil after frying. Mercadona says it can be reused in some cases, but food safety advice makes clear there are warning signs shoppers should not ignore.

How Spain households can make olive oil last longer without spoiling the pan

Olive oil has always had a special place in Spanish households. It goes on toast, into salads, over grilled vegetables and, for many families, into the frying pan. But after years of sharp price swings, that familiar bottle now gets treated with a little more caution.

Recent supermarket price trackers still show olive oil as a product many shoppers monitor closely, with some litre bottles in Spain sitting around the €4 to €5 mark and premium options costing more. The Ministry of Agriculture, Fisheries and Food also publishes dedicated oil consumption and price data because olive oil remains such a significant household staple in Spain.

Any advice on reusing olive oil usage is welcome in Spain, and Mercadona has recently promoted its online guide to choosing olive oil, while consumer advice from Spain’s Organisation of Consumers and Users (OCU) says frying oil can be reused if it is properly maintained. However, “can” doesn’t mean “always should”.

How reused olive oil should be stored before it goes back in the pan

OCU advises keeping frying oil away from light and heat, covering it to limit contact with oxygen and avoiding very high frying temperatures. Its guidance says oil kept in good condition can be reused several times, but only when the oil has not deteriorated.

It should be allowed to cool, strained to remove crumbs or food remains, then stored in a clean, covered container away from sunlight and heat. Leaving old oil open in a pan, especially with bits of batter, fish or breadcrumbs still floating in it, is where the saving starts to turn a little sour.

The food being fried also matters. Potatoes tend to leave fewer residues than breaded meat, croquetas or fish. Strong-flavoured foods can also carry their taste into the next batch, which is why oil used for boquerones is unlikely to be welcome in a plate of churros, however Spanish the experiment may seem to be.

When used olive oil should not be reused again

OCU advises changing oil when it looks reddish, foams, smells strange or produces too much smoke. Oil that has turned thick, dark, sticky or bitter should not go back into food.

Temperature is another key point. OCU recommends keeping frying oil between 160C and 175C in a fryer, noting that temperatures above 175C can favour the formation of acrylamide in some starchy foods, while temperatures below 160C can make food absorb more fat.

Spain’s Agency for Food Safety and Nutrition (AESAN), also highlights acrylamide as a substance that can form when foods such as potatoes, bread or biscuits are cooked at high temperatures. AESAN points to frying temperature and cooking methods as factors that influence how much acrylamide is formed.

The most accurate visual queue is that golden is better than brown. Burnt or heavily browned fried food is not just less pleasant to eat, it is also a sign that the oil and the food may have been pushed too far.

How to stretch olive oil safely before it reaches the bin

An easy save is to use a smaller pan, the right amount of oil and steady heat. This can reduce waste without needing to keep old leftover oil for too long. Overloading the pan lowers the temperature and can make food absorb more oil, which wastes money and usually gives worse results.

Keeping separate oil for different foods can also help. Oil used for potatoes may be easier to reuse than oil used for battered fish. Mixing different oils is best avoided unless the cooking purpose and heat tolerance are understood, because oils can degrade differently at frying temperatures.

There is also a difference between oil for frying and oil for raw use. Oil that has already been heated and filtered may still be acceptable for another frying session, but a line should be drawn for using it as garnish on salads, toast or drizzling over gazpacho. For this it is best to follow Spanish-suit and use fresh extra virgin olive oil. 

How used cooking oil should be thrown away in Spain

As easy and enticing as it may seem, when oil has reached the end of its useful life, the sink is the wrong place to dispose of it. Spain’s Ministry for Ecological Transition and the Demographic Challenge describes used cooking oils as household waste once they are discarded, while Madrid City Council warns that used vegetable oil should not be poured into the sink or toilet because the grease film can affect water oxygenation and later treatment.

The best option is to let the oil cool, pour it into a sealed bottle or container, and take it to a local used-oil collection point, recycling container or punto limpio, the municipal recycling facility used in Spain for waste that should not go into normal bins. Some towns also have mobile puntos limpios or specific used-oil containers.

There is a balance to be found in Spanish households regarding the use of olive oil during a cost of living crisis that is keeping people checking supermarket receipts and the prices of basic kitchen ingredients. Throwing away oil after one clean frying session isn’t necessary, but neither is chasing savings once the oil has changed. If it smells wrong, smokes too easily, foams, darkens or carries burnt bits, the bottle has done its job.