So this is not quite true about when leaded gasoline is used. It is generally used in track specific cars. Vintage cars have long been retrofitted to not need l

So this is not quite true about when leaded gasoline is used. It is generally used in track specific cars. Vintage cars have long been retrofitted to not need let it gasoline. If those vintage cars have not been retrofitted it's fine because they literally don't put enough stress on the engines to need it. But there are street legal cars that have a track mode which changes the tune on the car and bypasses the catalytic converters while in that mode. The optimized tune can require 100+ octane gas. The way this is typically achieved is by taking a 118 octane leaded gas that is sold at the race track and mixing it with a lower octane gas to get the octane rating you need for your tune. Leaded it gas is not actually required to do this. It's just what's used because it's, probably, cheaper than unleaded alternatives. Additionally with unleaded alternative fuels that have very high octanes they generally require a different tune on your car. Because even for racers you can get ethanol blended gas or even pure ethanol which has a high enough octane rating but the tune on your vehicle is different because how it burns in the engine is different. So typically changes like this don't really happen until there is legislation that pushes the conversion to happen. Which it is long past time for leaded gasoline to completely disappear in every aspect. If there is still some exceedingly limited niche then it needs to be sold as an additive which is controlled and you must show you have a need for this. Although I'm really not sure what that need would be at this point. Some small engine airplanes do still use leaded gas. I'm not sure if they still do this but as part of pre-flight checks on those small airplanes they would check the gas to make sure it is the correct gas for the plane and then just dump that out onto the ground after they validated it. There's literally no reason for piston engine aircraft to continue to use leaded gasoline either. Especially considering that aircraft are highly regulated with the number of hours that can be on an engine before it's torn down and rebuild. There is plenty of opportunity to update these to unleaded.