No longer with Aviation fuel. FAA allows unleaded AVgas now. And it isn't a hole, it is needed for anti-knock. Most General Aviation (GA) Planes really do run

No longer with Aviation fuel. FAA allows unleaded AVgas now. And it isn't a hole, it is needed for anti-knock. Most General Aviation (GA) Planes really do run on very basic carb systems (with magnetos!) and believe me, the Air Fuel (AF) mixture is a big deal when you are at 10,000 feet or so, especially when it is warm. When it's cold it's easier to fly, and also less lead is needed AFAIK.