2014 Cadillac ATS Owner Manual - Page 276

9-62 Driving and Operating If the vehicle has a yellow fuel cap, E85 or FlexFuel can be used in the vehicle. See E85 or FlexFuel on page 9-64. knocking noise, commonly referred to as spark knock, might be heard. If the octane is less than 87, a heavy knocking noise might be heard when driving. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. Otherwise, you could damage the engine. If heavy knocking is heard when using gasoline rated at 87 octane or higher, the engine needs service. Use of Seasonal Fuels Use summer and winter fuels in the appropriate season. Driving or starting could be affected if the incorrect fuel is used. Drive the vehicle with the engine running until the fuel is a half tank or less, then refuel with the current seasonal fuel. Prohibited Fuels Gasolines containing oxygenates, such as ethers and ethanol, as well as reformulated gasolines are available in some cities. If these gasolines comply with the previously described specification, Fuel Use of the recommended fuel is an important part of the proper maintenance of this vehicle. When driving in the U.S., to help keep the engine clean and maintain optimum vehicle performance, we recommend using TOP TIER Detergent Gasolines. See www.toptiergas.com for a list of TOP TIER Detergent Gasolines. Recommended Fuel If the vehicle has a 2.5L L4 engine or a 3.6L V6 engine, use regular unleaded gasoline with a posted octane rating of 87 or higher. If the octane rating is less than 87, an audible knocking noise, commonly referred to as spark knock, might be heard when driving. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. If heavy knocking is heard when using gasoline rated at 87 octane or higher, the engine needs service. If the vehicle has the 2.0L L4 engine, use premium unleaded gasoline with a posted octane rating of 91 or higher. You can also use regular unleaded gasoline rated at 87 octane or higher, but the vehicle's acceleration could be slightly reduced, and a slight audible