Aircarft engines are a whole different animal. They are similar, but very different to car engines. They use two plugs per cylinder, they have no emissions systems or cooling system, they are built to more demanding specs. and tolerances, and they run on leaded gas.

The problem with the early aviation synthetics was that they couldn't carry away the lead sludge that forms as a byproduct of combustion. As a result, they had to change the formula to include some "regular" oil that could carry away the lead.





Dave