higher tech auto oils, and the products like aeroshell 15W-50 is a better option
You would need to get expert advice but my reading is. The engine type certificate will spell out the oil required and to use any other voids the airworthiness in certificated aircraft. FAA AD 80-04-03 R2 requires Lycoming LW 16702 antiwear additive to be added to the oil of Lycoming O-320-H, O-360-E, LO-360-E, TO-360-E, LTO-360-E, TIO and TIGO-541 engines. Some oil manufactures have added this additive to their oils, so you need to check if you use one of these engines.
As you suggest aviation oils will no longer be formulated to deal with lead but also have other issues such as handling heat loads (air cooled engines typically run at nearly double the temp of an water cooled auto - which has viscosity implications also), auto engines run at low power whereas aviation spend their life at a constant high power (take off and cruise settings), auto oils also typically contain zinc and phosphorus. Ash deposits produced from these metal containing additives tend to form in the combustion chamber where they can cause pre-ignition. This in turn can lead to engine failure, hence aviation oils are formulated from metal free additives. Zinc will quickly destroy the master rod bearing of a radial for example and phosphorus is literally capable of dissolving your copper bearing material.
The reverse is also true in using aviation oil in automotive applications ie its not formulated to handle the requirements. Seems like oils aint oils as the ad used to say.