The difference between 95 and 92 gasoline: technical nuances

In normal mode, the combustion of the fuel-air mixture (FAC) in the cylinder is deflagration (smooth) in nature. Detonation is an explosive, spontaneous ignition of the TVS until the spark is given by the spark plug. The flame front propagates at supersonic speed, generating shock waves. Their cyclical effect leads to erosion of pistons, destruction of the crankshaft liners and local overheating of the cylinders.

The octane number is determined by comparative testing with reference mixtures of isooctane (OH = 100) and n-heptane (OH = 0). Russian gas stations indicate the octane number according to the research method (RON), which simulates moderate load modes of engine operation.

The need for high-octane fuel is directly dictated by the geometry and design of the engine:

Motors with a compression ratio of up to 9.5:1 are structurally adapted to the AI-92. The pressure and temperature at the end of the compression stroke are not sufficient to spontaneously ignite this fuel.

Units with a compression ratio of 10:1 (including most modern atmospheric and turbocharged engines) require AI-95 or AI-98. High detonation resistance prevents premature ignition under conditions of extreme compression.

Application of AI-92 in the engine requiring AI-95: Electronic control unit (ECU) fixes detonation using piezosensors and applies correction, shifting the angle of ignition ahead of the late side. This prevents instantaneous destruction of the internal combustion engine, but inevitably leads to a drop in torque, a decrease in efficiency and an increase in specific fuel consumption. Long-term operation in this mode is fraught with a reduction in motor resource.

Application of AI-95 in the engine, designed for AI-92: Technically safe. The margin of detonation resistance will be excessive, but the ECU algorithms will not be able to realize the potential benefits of such fuel. There is no economic feasibility of this action.

The only valid fuel selection criteria are the automaker's specifications as specified in the operating manual or on the fuel tank hatch. A deviation from the recommended octane number, especially downward, carries direct engineering risks for the technical condition of the power unit.