Chili oil is one of those ingredients you run across in a recipe from time to time, but never seem to have on hand. There are a few simple substitutions for chili oil. All you really need is a high quality cooking oil and something spicy, like ripe peppers or a bit of cayenne pepper.
Combine 1/4 tsp salad oil with a pinch of cayenne pepper. To make larger quantities of chili oil, use two parts salad oil to one part cayenne pepper--but most recipes only call for a few drops of chili oil due to its strong, spicy flavor and heat content.
Heat Chilies in Oil
Fresh chilies, such as Szhechuan or jalapeno, may be simmered in hot oil for about 30 minutes, then cooled and separated from the oil. The red, spicy oil can then be used as the substitute. If you choose an oil with a high smoking point, stir-frying the chilies in the hot oil for just a few minutes can also create an oil packed with heat and spice.
If you use a stable oil with a strong shelf life, placing dried chilies in a bottle of oil will work just fine as a stand-in for chili oil. This oil will have to steep for about 30 days before the flavor is fully released. Only use completely dehydrated peppers for this method. According to Oregon State University, using ripe or undried peppers can create a bacteria called Clostridium botulinum to arise in the oil. That bacteria is a form of food poisoning.
Crushed Red Peppers
Heating 1 tsp of crushed red pepper in a saucepan with about 1/4 cup of oil should also make a simple chili oil. Simmer the combination on low heat for about 10 minutes. Strain it and remove the seeds and flakes. This substitution is one you're most likely to already have the ingredients for, whether you cook regularly or enjoy eating out.