Should the Highlander use 92 or 95 octane gasoline?
2 Answers
According to the official vehicle manual recommendation, the Highlander should use 92 octane gasoline. In addition to checking the suitable gasoline grade in the vehicle manual, the Highlander's fuel cap also indicates the recommended octane rating. 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, while those with a compression ratio between 10.0-11.5 should use 95 octane gasoline. However, with the application of new technologies, the compression ratio alone cannot determine the appropriate gasoline grade, as high compression ratio engines can still be tuned to use lower octane gasoline. This is because other factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, the higher the gasoline octane rating, the higher the octane number 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 Highlander 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 number may alter the fuel's ignition point, leading to delayed combustion in the engine. This results in reduced engine power and thermal efficiency, with the practical experience being poorer performance. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Due to the significantly lower octane number, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires during the compression stroke, resistance will arise during the upward stroke. This resistance makes the engine run very unstably. If the knocking is imperceptible, it only increases noise without obvious engine damage. However, noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, and in severe cases, cylinder scoring.
As a frequent long-distance driver, I thoroughly researched fuel requirements before purchasing my Highlander. The specific version matters - the 2.0T turbocharged model strictly requires 95 octane, as clearly stated in both the manual and fuel cap. This manufacturer requirement stems from the engine's high compression ratio, where 95 octane provides better anti-knock performance. Long-term use of 92 octane may cause knocking and potentially lead to major engine repairs. The hybrid version with 2.5L engine can use 92 octane, offering some cost savings. My personal advice: don't cut corners - the 2.0T version should consistently use 95 octane from reputable gas stations. When unfamiliar with local stations, it's worth driving further to find trusted fuel providers.
