You must consult your owner's manual. This will give you the precise gap specification recommended by the manufacturer for your particular Cutlass.
Failing that, you can:
* Check the spark plug packaging: If you've recently bought replacement spark plugs, the packaging will often specify the correct gap.
* Consult a repair manual: A Haynes or Chilton repair manual for your specific year and model Cutlass will contain this information.
* Ask a parts store professional: Take your old spark plugs to an auto parts store. They can often identify the correct gap for your engine based on the plugs or your vehicle's information.
Do not guess. An incorrect spark plug gap can lead to misfires, poor performance, and engine damage.
