Cooking oils are one of the most quietly confusing aisles in the supermarket. Every bottle claims to be the healthiest, the most authentic and the best for high heat. Most of that is marketing. In practice, three oils will cover almost everything a normal home cook does, and you can ignore the other twenty.
The two things an oil is judged on
When you choose a cooking oil, only two properties really matter for the pan: its smoke point and its flavour. The smoke point is the temperature at which the oil starts to break down, smoke, and taste bitter. A refined neutral oil like sunflower or vegetable oil smokes at around 230°C and takes high-heat cooking easily. Extra-virgin olive oil smokes at around 190°C and will turn acrid if you push it too hard. Butter smokes early because of its milk solids.
Flavour is the second axis. Extra-virgin olive oil tastes strongly of olive; refined oils taste of almost nothing; sesame oil tastes of sesame; ghee tastes of caramelised butter. Pick the oil whose flavour either helps the dish (olive oil in a Mediterranean sauté) or disappears into it (neutral oil in a stir-fry).
The three oils you actually need
A workable everyday oil shelf has three bottles on it. One neutral, high-smoke-point oil for frying, searing and roasting — sunflower, rapeseed (canola), or refined vegetable oil all work fine and are cheap. One good extra-virgin olive oil for finishing, dressings and gentle sautés — spend a bit more on this one; you will taste it every day. And one flavoured oil for the cuisine you cook most — toasted sesame oil if you cook a lot of Asian food, or a really good peppery Tuscan olive oil if you cook a lot of Italian.
That is genuinely it. Coconut oil, avocado oil, walnut oil and grapeseed oil all have specific uses, but none of them is essential to have on hand for weekly cooking.
What to fry in
For anything above a gentle sizzle — stir-fries, deep-frying, high-heat roasting, searing steak — use a refined neutral oil. Its neutral flavour lets the food taste of itself, and its high smoke point means it will not burn before the food browns. Extra-virgin olive oil at 220°C in a wok is a waste of expensive oil and produces slightly bitter food. Save it for the finish.
For moderate-heat cooking — softening onions, sweating vegetables, making pasta sauces — extra-virgin olive oil is a good choice because its flavour is a positive contribution and the temperature never gets high enough to hurt it. Butter is also excellent here, especially mixed with a splash of oil to raise its effective smoke point.
What to finish with
Finishing oils are the ones you drizzle at the end. This is where flavour matters most because heat has not muted it. A few drops of really good extra-virgin olive oil on a bowl of soup, a plate of grilled vegetables, or a piece of fish is the difference between a plain meal and a memorable one. Toasted sesame oil does the same job for stir-fries — a small splash at the very end, off the heat, adds a nutty top note that no other ingredient can replicate.
The rough rule is: expensive oil goes at the end, cheap oil does the cooking. Reverse that and you are burning money and dulling flavour at the same time.
Storage and shelf life
Oil goes off. It rarely tastes obviously rancid, so most home cooks do not notice, but stale oil tastes flat and slightly cardboardy. Store all oils away from light and heat — a cupboard, not the counter above the stove. Buy oil in quantities you will use in three to six months. Extra-virgin olive oil is worst affected by age; a bottle you opened last summer is probably past its best. If in doubt, smell it — good oil smells fresh and grassy; stale oil smells like old crayons.
Reusing frying oil
Oil used to deep-fry can be reused two or three times if you strain it through a fine sieve while still warm and store it in a sealed jar in a cool cupboard. Do not reuse oil that has cooked strongly flavoured foods (fish, garlic) with oil for a different job. Discard when it looks dark, smells off or foams up when heated.
The health question, briefly
Every year a different oil is declared the healthiest and a different one is declared toxic. In reality, using a moderate amount of extra-virgin olive oil, a moderate amount of refined vegetable oil for high-heat cooking, and a small amount of butter for flavour is a fine, unremarkable choice supported by decades of ordinary dietary science. Do not obsess. The bigger levers on your health sit elsewhere — vegetables on the plate, portion sizes, how often you cook at home at all.
Cook Max recipes call for whichever oil suits the dish. If a recipe says "neutral oil", any refined vegetable, sunflower or rapeseed oil will do; if it says "olive oil", it means extra-virgin, added early enough to soften onions but not hot enough to burn.