Adding vinegar directly to hot oil is generally not recommended due to the potential for splattering and a harsh, acrid flavor. It's better to add vinegar towards the end of the cooking process or after removing the food from the heat.
Vinegar is primarily water and acetic acid. When added to hot oil, the water content can cause the oil to splatter violently, posing a safety risk. Furthermore, the high heat can quickly evaporate the volatile acids in the vinegar, resulting in a sharp, unpleasant taste that overpowers other flavors.
Instead of adding vinegar directly to hot oil, consider these alternatives:
If you must add vinegar to hot oil, do so very carefully and in small amounts. Remove the pan from the heat source first, and add the vinegar slowly while stirring constantly. Be prepared for splattering and wear appropriate safety gear, such as an apron and eye protection.