Red Seal Automotive Service Technician Practice Exam 2025 - Free Automotive Technician Practice Questions and Study Guide

Using the wrong fuel type in a vehicle can lead to engine knocking, which is a result of improper combustion within the engine. Each engine is designed to operate optimally with a specific fuel grade that matches its compression ratios and ignition timing. When a lower-octane fuel is used in an engine that requires a higher-octane fuel, it can lead to pre-ignition and misfire, causing knocking sounds. This happens because the fuel ignites too early in the combustion cycle, which can not only impair performance but also lead to serious damage over time if left unchecked.

In contrast, improved engine efficiency, enhanced fuel economy, and reduced exhaust emissions are outcomes typically associated with using the correct fuel type. These benefits arise from optimal combustion processes and engine operation that leverage the characteristics of the fuel for cleaner and more efficient performance. Therefore, using the correct fuel type is crucial not only for performance but also for the long-term health of the vehicle's engine.