[Manute]

Maybe you are right,but here are a few factors that made auto gas not an option.For example,the older planes here are no more than about 35-40 years old,and the actual engines are all modern,so a 35 yearl old piper mounts a,not more than 2 year old engine...Thatīs because itīs not common to overhaul them,when an engine reaches overhaul time,say at 2000 hours,then the engine is replaced with a new one.And itīs very common to see cherokeeīs 140 with the newer 160 warriorīs engines.And this engine can afford the avgas 100LL....people did itīs schedule,with no problems.And think that,in modern engines,lycoming or continental voids most of the warranties if you use auto gas because,true or not,legally they donīt respond in most of the cases.At least,as far as I have read here.
And also,flight schools,the majority users,get discounts on avgas, making auto gas actualy more expensive.
Maybe the hot temperature here help,but for sure i didnīt saw overhauls on engines with 400 hours...something like that would make us think the engine is defective.
One thing is sure,maybe you are right,because private aviation here costs about triple than there...