According to the official vehicle manual recommendation, the 2021 RAV4 should use 92 octane gasoline. For the 2021 RAV4, besides checking the appropriate gasoline grade in the vehicle manual, you can also find it on the fuel tank cap, which will be clearly marked. Typically, the gasoline grade can also be determined based on the engine's compression ratio. Vehicles with an engine compression ratio between 8.6-9.9 should use 92 octane gasoline, those between 10.0-11.5 should use 95 octane gasoline, and if the compression ratio is higher, 98 octane gasoline is recommended. However, with the application of new technologies, the gasoline grade cannot be solely determined by the compression ratio. High compression ratio engines can also be tuned to use lower octane gasoline because, apart from the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, the higher the gasoline octane number, the higher the octane value and the better the anti-knock performance. 92 octane gasoline contains 92% isooctane and 8% n-heptane, while 95 octane gasoline contains 95% isooctane and 5% n-heptane. If the 2021 RAV4 occasionally uses the wrong gasoline grade, simply switch back to the correct grade after consumption. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower octane gasoline, using higher octane gasoline will not cause damage, but the increase in octane value will alter the fuel's ignition point, leading to delayed combustion in the engine. This means both the engine's power output and thermal efficiency will decrease, resulting in poorer performance. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Because the octane value is too low, the gasoline's ignition point decreases, causing it to ignite prematurely during the compression stroke. If combustion occurs before the spark plug ignites during the compression stroke, resistance will arise during the upward stroke. This resistance makes the engine run very unstably. If it's only mild knocking, the main effect is increased noise with no significant damage to the engine. However, if there is noticeable knocking, it indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, and in severe cases, cylinder scoring.
