What are the consequences of using 92-octane gasoline in a Golf?
3 Answers
According to the official vehicle manual recommendation, the Golf should use 95-octane gasoline. Occasionally using 92-octane gasoline is acceptable as long as you switch back to the correct octane rating afterward. However, prolonged use of the wrong gasoline octane can have the following effects: For vehicles recommended to use lower octane gasoline, accidentally using higher octane gasoline will not cause damage. However, the increased octane rating alters the fuel's ignition point, leading to delayed combustion in the engine. This results in reduced engine power output and thermal efficiency, with the practical experience being noticeably poorer performance. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Since the octane rating is significantly lower, the reduced ignition point causes premature combustion during the compression stroke. If the fuel ignites before the spark plug fires during the compression stroke, resistance occurs in the upward stroke. This resistance makes the engine run very unevenly. If the knocking is imperceptible, it only increases noise without obvious engine damage. However, noticeable knocking indicates severe engine operating conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, with severe cases potentially leading to cylinder scoring. In addition to checking the appropriate gasoline octane in the vehicle manual, Golf owners can also find this information on the fuel filler cap, which is usually labeled. Typically, the gasoline octane can also be determined based on the engine's compression ratio. Vehicles with a 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 required gasoline octane. High compression ratio engines can be tuned to use lower octane gasoline 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 octane, the higher the octane rating 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.
When I used to drive a Golf, my friend suggested I try 92-octane fuel to save money, but the engine noise became extremely loud, like firecrackers in a tin can. The technician at the 4S shop explained that using lower-octane fuel in high-compression engines can cause knocking, and the sensors automatically retard ignition timing, leading to sluggish power and poor acceleration. Long-term use of 92-octane fuel can also cause carbon buildup in the fuel injectors. Last year, my neighbor's Golf had a major repair costing over 5,000 yuan due to this issue. Now, I always make sure to use 95-octane fuel—the money saved on fuel isn't worth the repair costs. It's just not a good trade-off.
Based on a decade of driving experience, putting 92-octane fuel in a Golf is like giving an athlete cheap energy drinks. Engines with a compression ratio above 10 require high anti-knock fuel, and 92-octane has a lower rating than 95, causing premature self-ignition of the air-fuel mixture in the cylinders and generating shockwaves. Although the ECU can adjust the ignition timing to compensate, the power output becomes noticeably sluggish, and the engine revs up painfully slowly even when flooring the accelerator. I've tested two full tanks for comparison—92-octane consumed 1.2 liters more per 100 kilometers than 95. Worse yet, accelerated carbon buildup increases piston ring wear. I've seen cases where engines started burning oil after just 30,000 kilometers.
