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The Hidden Dangers of Low-Octane Petrol: How it Harms Your Car and Causes Poor Fuel Consumption

Your car is a finely tuned machine, and what you put into it matters. While it's tempting to opt for cheaper, low-octane petrol to save a few dollars at the pump, doing so can have detrimental effects on your vehicle's performance and fuel economy. In this blog, we'll explore the hidden dangers of low-octane petrol and how it can harm your car while causing bad fuel consumption.

Understanding Octane Ratings:

Before delving into the risks associated with low-octane petrol, it's essential to understand what octane ratings represent. Octane rating is a measure of a fuel's resistance to knocking or pinging during combustion. Higher-octane fuels have greater resistance to premature ignition, allowing them to withstand higher compression ratios without detonating prematurely.

1. Engine Knocking and Performance Issues:

Low-octane petrol has a lower resistance to knocking, which occurs when the air-fuel mixture ignites prematurely in the engine's cylinders. Engine knocking can lead to a rough-running engine, reduced power output, and overall poor performance. Continued use of low-octane petrol can exacerbate these issues and potentially cause long-term damage to engine components.

2. Reduced Fuel Efficiency:

One of the most significant drawbacks of using low-octane petrol is its impact on fuel efficiency. When your engine experiences knocking or pinging due to the use of low-octane fuel, it compensates by adjusting its timing and fuel delivery, which can lead to increased fuel consumption. Over time, this can result in significantly poorer fuel economy, costing you more money at the pump in the long run.

3. Increased Emissions:

In addition to harming your car's performance and fuel efficiency, low-octane petrol can also contribute to higher emissions. When the engine is forced to adjust its timing and fuel delivery to compensate for knocking, it may produce more pollutants, such as carbon monoxide and nitrogen oxides. These harmful emissions not only negatively impact the environment but can also lead to regulatory compliance issues for vehicle owners.

4. Engine Deposits and Build-Up:

Low-octane petrol may contain fewer detergents and additives compared to higher-octane fuels, which can lead to the accumulation of deposits and carbon build-up inside the engine. These deposits can restrict airflow, interfere with combustion, and ultimately degrade engine performance over time. Regular use of low-octane petrol can exacerbate this problem, leading to costly repairs and maintenance down the road.

5. Potential Engine Damage:

Continued use of low-octane petrol in engines designed for higher-octane fuels can result in severe damage over time. Prolonged engine knocking and detonation can cause piston damage, cylinder head damage, and other internal engine components to fail prematurely. Repairing or replacing these damaged parts can be expensive and may require extensive labor.


While opting for low-octane petrol may seem like a cost-saving measure in the short term, it can lead to a host of long-term issues that outweigh any potential savings. From engine knocking and reduced fuel efficiency to increased emissions and potential engine damage, the risks associated with using low-octane petrol far outweigh the benefits. To ensure optimal performance, fuel efficiency, and longevity for your vehicle, it's essential to use the fuel recommended by the manufacturer and avoid the temptation of low-quality alternatives. Remember, investing in quality fuel today can save you from costly repairs and headaches tomorrow.

Talk to McMahon Automotive today if you have any concerns about fuel consumption with your vehicle.

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