Is it mandatory to use 95-octane gasoline for the Highlander?

[DiAlexa]

The Highlander does not necessarily require 95-octane gasoline. It has 9 currently available models, with some like the 2022 Hybrid 2.5L 2WD Elite 7-seater using 92-octane gasoline, while others like the 2021 2.0T 4WD Premium 7-seater require 95-octane gasoline, as recommended in the vehicle's official user manual. In addition to checking the appropriate gasoline grade in the user manual, the Highlander's fuel cap also indicates the recommended octane rating. Generally, the engine's compression ratio can also determine the suitable gasoline grade: vehicles with a compression ratio between 8.6-9.9 should use 92-octane gasoline, those between 10.0-11.5 should use 95-octane, and higher ratios may require 98-octane. However, with modern technologies, the compression ratio alone may not dictate the gasoline grade, as high-compression engines can sometimes be tuned for lower-octane fuel. Other factors like ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Typically, higher-octane gasoline has a higher concentration of isooctane, which improves anti-knock properties. For example, 92-octane gasoline contains 92% isooctane and 8% n-heptane, while 95-octane gasoline contains 95% isooctane and 5% n-heptane. Occasionally using the wrong gasoline grade in the Highlander only requires switching back to the correct grade after the tank is empty. However, prolonged use of the wrong grade can have the following effects: Using a higher-octane gasoline in a vehicle designed for lower octane may not cause damage, but the increased octane can alter the fuel's ignition point, leading to delayed combustion. This reduces engine power and thermal efficiency, resulting in poorer performance. Using lower-octane gasoline in a high-octane vehicle can cause engine knocking. The significantly lower octane reduces the ignition point, causing premature combustion during the compression stroke. If detonation occurs before the spark plug fires, it creates resistance during the piston's upward stroke. This resistance makes the engine run unevenly. Mild knocking may only increase noise without significant engine damage, but severe knocking indicates serious engine issues, affecting driving stability and causing abnormal wear on pistons and cylinders, potentially leading to cylinder scoring.