What happens if you put 92 gasoline in a car that requires 95?
3 Answers
Using 92 gasoline in a car that requires 95 can damage the pistons or cylinders, potentially leading to engine failure. The difference between 92 and 95 gasoline lies in their isooctane content: 92 gasoline contains 92% isooctane, while 95 gasoline contains 95%. Additionally, the anti-knock properties of these fuels differ. Anti-knock refers to the resistance to knocking, which is an abnormal combustion phenomenon in gasoline engines. The anti-knock property indicates a gasoline's ability to resist knocking under various operating conditions, measured by octane rating—higher octane means better anti-knock performance. The anti-knock capability of gasoline is related to its chemical composition.
I often hear car enthusiasts discussing this issue. If a car that requires 95-octane fuel is filled with 92-octane fuel, the most immediate problem is insufficient anti-knock performance. High-compression engines need high-octane gasoline to suppress knocking. The lower octane rating of 92-octane fuel makes the air-fuel mixture in the cylinder more prone to premature ignition. This causes the engine to produce a metallic knocking sound, and the power output becomes inconsistent. Although you might not notice obvious abnormalities in the short term, driving like this for a few hundred kilometers will accelerate wear on the piston rings and cylinder walls, and spark plug carbon buildup will also occur faster. Once, my friend accidentally filled his turbocharged car with 92-octane fuel, and after just two tanks, the check engine light came on. Diagnostics showed a knock sensor alarm. In the long run, the money saved on fuel won’t cover the cost of engine repairs—it’s just not worth it.
From a cost-saving perspective, switching from 95 to 92 octane fuel may seem to save a few cents per liter, but the actual cost is much higher. Vehicles requiring 95 octane are typically turbocharged or high-performance engines, and 92 octane's combustion speed doesn't match their design parameters. Short-term effects include difficulty in cold starts, sluggish throttle response during acceleration, and noticeable power deficiency when overtaking. I once accidentally refueled with 92 octane at a highway service area, and my fuel consumption increased by about 10% compared to normal. To adapt to lower-octane fuel, the engine retards ignition timing, resulting in less efficient power output and higher fuel consumption. For cars over three years old, valve carbon buildup worsens, and a single carbon cleaning can cost as much as half a year's fuel price difference. Long-term use of lower-octane fuel can also damage the catalytic converter and oxygen sensors, with repair bills far exceeding any savings on fuel costs.
