If you’ve ever been tempted to fill up with the lowest-priced petrol at the pump, you’re not alone. With rising living costs across Australia, it's natural to look for ways to save money. But when it comes to fuel, the cheapest option may not be the most economical in the long run. Using low-quality or cheap fuel can quietly damage your engine over time, leading to costly repairs and reduced performance. In this blog, we’ll explore exactly why that happens—and what you can do to protect your car.

What Defines "Cheap" Fuel?

Cheap fuel doesn't necessarily mean it’s unsafe. But in many cases, lower-cost fuels lack important additives that help clean your engine and keep it running smoothly. Premium fuels, such as those sold by major Australian fuel retailers, often contain detergents that remove carbon deposits. Budget options may skip these additives, allowing long-term buildup that harms performance.

Another issue is inconsistency. Smaller or independent stations may not maintain their underground fuel tanks as strictly as major brands. Over time, water, rust, or sediment can contaminate fuel, which can then make its way into your car’s engine.

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Impact on Engine Components

Your engine is designed to run on a specific fuel quality. Using low-grade or contaminated petrol can negatively affect several engine components:

Fuel Injectors

Cheap fuel may leave carbon deposits in the injectors. Over time, these deposits can clog them, disrupting fuel flow and affecting both performance and fuel economy.

Combustion Chambers

Without cleaning additives, carbon buildup can occur in the combustion chambers. This disrupts how efficiently fuel burns, often causing knocking—which can damage engine parts.

Valves and Spark Plugs

Deposits can also build up on valves and spark plugs, leading to rough idling, misfires, and hard starts, especially on cold mornings.

Reduced Fuel Efficiency and Performance

One of the first signs of using poor-quality fuel is lower mileage. Drivers often report using more petrol than usual after switching to a cheaper brand. Your car might also feel sluggish, with delayed acceleration or reduced power when driving uphill or towing—a common scenario on Australian road trips or regional highways.

Increased Emissions

A dirty engine doesn't just cost you more in fuel—it also affects the environment. Incomplete combustion due to clogged injectors or dirty chambers releases more harmful emissions, such as hydrocarbons and carbon monoxide. This could be an issue if you’re subject to roadside vehicle emissions checks, especially in states like Victoria or New South Wales where environmental standards are getting stricter.

Long-Term Damage and Costly Repairs

While a few cents per litre might seem like a saving, cheap fuel can lead to expensive repairs. Below is a general guide to what repairs could cost in Australia:

As you can see, a $5 saving at the pump can quickly turn into a multi-thousand dollar expense.

Tips to Avoid Engine Damage from Fuel

Here’s how to protect your engine while still being cost-conscious:

Stick to Major Fuel Brands

Trusted names like BP, Caltex, Shell, and Ampol generally maintain high fuel quality standards and storage practices. Many offer rewards or discount programs that make their prices competitive with independent operators.

Use Premium Unleaded if Recommended

If your car's manual recommends or requires 95 or 98 RON (octane), stick with that. Using regular 91 RON in a car designed for premium can hurt performance and long-term reliability.

Use Fuel System Cleaners

Every 5,000 to 10,000 km, consider using an Australian-approved fuel system cleaner to help prevent build-up in injectors and valves.

Watch for Warning Signs

If you notice poor acceleration, a drop in fuel efficiency, or knocking noises, stop using the fuel in question and see your mechanic. These could be early signs of damage.

FAQs

Can I mix cheap fuel with premium petrol?
Yes, but it dilutes the benefits of premium additives. It’s better to stick with one consistent fuel grade for best results.

How do I know if fuel is damaging my engine?
Watch for sluggish acceleration, reduced mileage, engine knocking, or a check engine light on your dashboard.

Are all cheap fuels bad?
Not necessarily. Some independent stations meet high standards. But without consistent regulation or fuel testing, it’s a risk.

Is premium fuel worth it for all cars?
Not for every vehicle. Check your owner’s manual. But even standard cars can benefit from higher-quality fuel with cleaning agents.

How often should I use a fuel additive?
About every 5,000 to 10,000 km, especially if you often use budget fuel or drive in stop-start city traffic.

Conclusion

It might be tempting to save a few dollars per tank by choosing cheaper fuel, but the long-term risks aren’t worth it. From reduced mileage to serious engine damage, low-quality petrol can quietly erode your car’s performance and reliability. Investing in fuel from trusted Australian brands and following a few simple maintenance tips can help you avoid costly repairs and keep your vehicle running efficiently. A little care at the bowser today can save you thousands down the road.