Can I Use 92 After Running Out of 95?
2 Answers
It is acceptable to occasionally use 92 after running out of 95. Occasionally using the wrong gasoline grade only requires switching back to the correct grade after consumption. However, prolonged use of the wrong gasoline grade can have the following effects: For vehicles designed for lower grades, using a higher grade gasoline will not cause damage, but the increase in octane rating will alter the fuel's ignition point, leading to delayed combustion in the engine. This results in reduced engine performance and thermal efficiency, with the practical experience being poorer power output. For vehicles designed for higher grades, using a lower grade gasoline can cause engine knocking. Because the octane rating is significantly lower, the reduced ignition point may cause premature ignition during the compression stroke. If combustion occurs before the spark plug fires during the compression stroke, resistance will arise in the upward stroke. This resistance makes the engine run very unstably. If the knocking is imperceptible, it may only increase 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. In addition to checking the recommended gasoline grade in the car's manual, you can also find it on the fuel tank cap. Typically, the gasoline grade can also be determined based on the engine's compression ratio. Cars with a compression ratio between 8.6-9.9 should use 92 gasoline, those between 10.0-11.5 should use 95 gasoline, and those with higher compression ratios should use 98 gasoline. However, with the use of new technologies, the compression ratio alone cannot determine the appropriate gasoline grade, as high compression ratios can also be tuned to use lower-grade gasoline. 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 rating and the better the anti-knock performance. 92 gasoline contains 92% isooctane and 8% n-heptane, while 95 gasoline contains 95% isooctane and 5% n-heptane.
When I used to work on cars, I often encountered this type of issue. The main difference between 95 and 92 is the octane rating, which affects anti-knock performance. If your car's manual explicitly requires 95-octane fuel, then using 92 long-term is definitely not advisable. Lower-octane fuel can cause engine knocking, resulting in a pinging sound from the cylinders, and prolonged use can damage pistons and cylinders. However, in special circumstances, such as remote gas stations only having 92, using it once in an emergency isn't a big deal. After filling up, avoid aggressive acceleration and drive gently to prevent high engine load. Once the fuel gauge is near empty, refill with 95-octane fuel as soon as possible. Remember, occasional mixing isn't a major issue, but don't make it a regular practice—saving a few cents now might cost you big on engine repairs later.
