I’ve read a ton of stuff over the last couple years on cooking oils — some highly credible and research-based, some full of witch-doctory, all extremely sure of itself. I have developed some opinions, naturally, both as a person interested in nutrition and as a home cook whose chief priority is making tasty food. Here are the top things I think about when deciding what oil to use:
1. My current go-to all-purpose cooking oil, if I had to pick just one, is avocado oil. It’s a monounsaturated oil like olive oil, and (unless you’re buying a farm-to-table bright green version) it has a very neutral taste and smell. You can cook with it, use it in baking, or make it into salad dressing — definitely a jack of all trades. Having said that…
2. You can use olive oil, coconut oil, or ghee for just about anything, and the results will also be delicious. Sure, they each have a distinct aroma and might go especially well with certain recipes, but don’t fuss too much about what oil to use. If your recipe calls for one, and you substitute in another, just take note of any difference and see what you think, but don’t worry that it’s going to “ruin” your results. Sometimes a little hint of different makes it that much better.
3. The above four oils are the ones I use. I like sesame oil and peanut oil just fine, too, but I no longer bother to buy them. Oil has a shelf life — it needs to get used. Ideally you want to use up that newly opened bottle of olive or avocado oil in, say, three to six months. (Depends on how big your bottle is, right?) Monounsaturated fats aren’t quick to oxidize and turn rancid, but they won’t stay good forever. (You’ll know when it’s gone off, as rancid oil has a distinct musty odor. Trust me, you will notice.) Coconut oil and ghee are both rich in saturated fat, which makes them shelf stable for longer — making either a good pantry back-up option.
4. In general, buy oils in glass jars or bottles. I don’t make this an absolute rule (e.g. we buy big bulk containers of coconut oil from Costco, which are plastic), but I definitely would prefer glass wherever it’s an option, especially for liquid oils. I think there’s both a campaign of misinformation defending plastics and a circus of “clean eating” scare-tactic nonsense around the dangers of plastics, and I have no idea where the truth lies. But have you ever pulled an old, cheap bottle of oil out of the back of a cabinet, and it’s weirdly sticky and crumply? That’s the result of the oil slowly degrading the plastic as they sit in contact. Oils and plastics seem to interact in some funky ways. This is a non-issue with glass.
5. Don’t worry too much about cooking temperature. It’s true that a really good olive oil will be most nutritious unheated, but you’re not going to “ruin” it by using it to cook. Use what you’ve got. To get the most virtue out of your cooking oils (and your food in general), don’t cook over high heat. High heat is for boiling water. If you’re sauteing or pan-frying, medium to medium-high heat is all you need. I prefer coconut oil or ghee for frying, but I consider that a matter of taste. If you’re roasting oil-tossed veggies or potatoes in the oven, no need to crank it up to 400F+. You can roast veggies beautifully at 350F, better for the veggies and the oil you’re using to roast them. All the high-heat warnings around oil aren’t so much a warning about the oil as they are an indicator that cooking at very high heat is hard on food.