Should the Older Model LaCrosse Use 92 or 95 Octane Gasoline?
1 Answers
According to the official vehicle manual recommendation, the older model LaCrosse should use 92 octane gasoline. In addition to checking the suitable gasoline grade in the vehicle manual, you can also find it indicated on the fuel tank cap of the older model LaCrosse. 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 some new technologies nowadays, the gasoline grade cannot be solely determined by the compression ratio. Even engines with high compression ratios can be tuned to use lower octane gasoline. This is because, besides the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, the higher the gasoline grade, 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 older model LaCrosse 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 by mistake will not cause damage, but the increase in octane number 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 as experienced in real feedback. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Because the octane number is significantly lower, the reduced ignition point of the gasoline may cause premature ignition 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 with increased noise, the damage to the engine is not significant. However, if noticeable knocking occurs, it indicates severe engine operating conditions. The vibrations not only affect driving stability but can also cause abnormal wear on the pistons and cylinders, and in severe cases, even cylinder scoring.
