Higher octane gas has compounds which reduce knock. Knock is when gas ecplodes rather than burn. When gas ecplodes head gaskets fail or engine blows up. The reason for knock is the air to fuel ratio is too high. This happens when there is either to much air or too little fuel. Turbo chargers add air. Run 93 octane unless you drive like grandma or Grandpa.I have a new 2019 Regal with a 2 liter turbo. The owners manual say 93 octane fuel is recommended but 87 is OK. Should the high octane be used and why?