Which type of cooking oil best for weight loss?

Several: Use a monounsaturated or polyunsaturated oil, and as little as possible. Drain the food after cooking and eat as little fried food as possible since it's generally high fat and high calorie items that are fried. Avoid animal fats which are saturated, and don't reuse oil as cooking saturates even the best unsaturated oil after a short period of time or high heat.