According to the official vehicle manual recommendation, the GL8 Fathead Fish should use 95 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual for the GL8 Fathead Fish, you can also find it on the fuel tank cap, which will also indicate the recommended grade. Generally, 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 choose 92 octane gasoline, while those with a compression ratio between 10.0-11.5 should opt for 95 octane gasoline. However, with the use of some new technologies, the gasoline grade cannot be determined solely based on the compression ratio. High compression ratios can also be tuned to use lower-grade 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 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 GL8 Fathead Fish occasionally uses the wrong gasoline grade, simply switch back to the correct grade after use. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended for lower grades, using higher-grade gasoline will not cause damage, but the increase in octane number will change 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 in practice. For vehicles recommended for higher grades, using lower-grade gasoline can cause engine knocking. Because the octane number 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 appear during the upward stroke. This resistance will make the engine run very unstably. If it's mild knocking, it only increases noise and does not significantly damage the engine. However, if there is noticeable knocking, it indicates severe engine conditions. The vibration not only affects driving stability but can also cause abnormal wear on the pistons and cylinders, and in severe cases, cylinder scoring.
