Regular gasoline is adequate for most sedans and subcompact cars. But drivers of luxury vehicles, like BMWs or Mercedeses, or sports cars should check their owners’ manuals, which typically recommend premium gasoline, says Mark Scott, spokesman for Autotrader.com, a comparison shopping site for cars. (Newer models often list this information on the gas cap or inside the gas door, as well.) Pass on the recommended gas and your car’s performance will decrease.
A lower-octane fuel may also cause a knocking sound in a high-performance vehicle. That generally means the gas is igniting before the motor is in the right position, a problem that can damage your engine, Sinclair says.