Warning: Using 91 Octane Instead of 95 Causes Knocking, Pre-Ignition, and Engine Whining Noise

The appearance of a whining or humming noise while driving is a phenomenon that worries many car owners, especially when it increases with speed or when pressing the accelerator. Although some may attribute these sounds to road conditions or tires, they often serve as an early warning of a mechanical issue that requires quick inspection and diagnosis.

Common Causes of Whining Noise

In this context, Walid Abdo, manager of a car maintenance center, confirmed in exclusive statements to Al-Ahram Auto that the whining noise often appears during hard acceleration, when the car is loaded with extra weight, or while climbing hills. It may also be noticed during turns or at specific speeds.

Abdo explained that among the most prominent potential causes of this problem are faults in the wheel and tire system. He noted that increased noise with higher speed could be due to damaged wheel bearings, imbalanced wheels, uneven tire wear, or a problem with the braking system. He added that ignoring these symptoms could lead to worsening faults and may even affect vehicle stability and ease of control while driving.

Differential Oil Deficiency

He also pointed out that low differential oil is a common cause, especially in cars with rear-wheel drive or all-wheel drive systems. He noted that whining noise occurring only when pressing the accelerator often indicates a problem related to the differential, which relies on special oil to reduce friction between gears. If the oil level is low or there is a leak, clear sounds may appear accompanied by slight vibrations and heaviness in vehicle movement, along with the possibility of gear damage over time.

Combustion Issues and Improper Fuel Use

Abdo added that some cases of whining are linked to a fault in the combustion process inside the engine, especially during load pulling or sudden acceleration. This condition can result from using fuel that does not match the engine specifications, carbon deposit buildup inside the combustion chambers, engine overheating, or a fault in the exhaust system or its related sensors.

He explained that using low-octane fuel in engines requiring higher octane levels can lead to pre-ignition or knocking, a condition that produces abnormal sounds inside the engine and negatively affects performance and efficiency.

Difference Between 91 and 95 Octane

Regarding the difference between 91 and 95 octane gasoline, Abdo clarified that the key difference lies in the fuel's ability to resist pre-ignition inside the engine. 95 octane has a higher octane rating, making it more resistant to pre-ignition and more suitable for high-compression engines. Using 91 octane in engines that require 95 can lead to knocking and pre-ignition, causing abnormal sounds and reducing engine efficiency.