95 Unleaded Or 93 Unleaded Petrol? Which One Is Better?

95 unleaded or 93 unleaded? We are asked this question every time we refuel. But many of us don’t even know the difference. Michanic compares the two to help you choose what’s best for your car.

95 Unleaded vs 93 Unleaded

During tough times we are always looking for ways to save money. And the 29c saving that 93 unleaded offers might have you wondering if you should switch fuel type.

The 95 and 93 numbers refer to the octane rating in each of the two fuels. The higher the number, the higher the octane rating. The pistons in your car’s engine compress a cylinder with a mixture of fuel and air before the spark plug ignites it. The octane rating represents the extent to which the fuel can be compressed before spontaneously igniting. Higher octane fuel is more stable, can undergo more compression and produces better efficiency and power. However not all vehicles require or benefit from higher octane fuel. Deciding between 95 unleaded and 93 unleaded for your car depends on a few factors:

Altitude

Atmospheric pressure has a significant impact on the in-cylinder pressures of naturally aspirated engines. Joburg is roughly 1700 metres above sea level, meaning the atmospheric pressure is about 17% lower than Durban or Cape Town which are at sea level. So, atmospheric pressure alone impacts the pressure within the engine cylinders. This is why there is a drop in engine performance inland when compared to the coast. At higher altitudes the lower atmospheric pressure lowers the tendency of the engine to knock, and the octane rating required decreases. If you are at the coast however, given the higher atmospheric pressure you should use the higher octane 95 unleaded fuel.

Car Type and Performance

Your car’s engine compression ratio determines what octane fuel you should fill your car up with. Engines with high compression ratios have more horsepower and require a higher octane fuel. 95 unleaded has a higher compression peak and serves to increase the car engine’s performance. The more stable higher octane fuel reduces the risk of igniting, allowing better performance and efficiency. Pre-ignition at high pressure can damage your engine (knocking). If you have a high performance car you should opt for 95 unleaded.

For newer car models, high performance cars typically have turbo-charged engines whereas standard cars are naturally aspirated. South Africa has many more naturally aspirated cars than newer turbo-charged cars on the road. Turbo-chargers boost the air pressure entering the combustion chamber, increasing pressure. Most high performance cars have turbo-chargers and require higher octane 95 unleaded fuel, while common naturally aspirated cars will run well on 93 unleaded. It’s highly unlikely that a standard car will see any performance gain by using 95 unleaded. So, unless your engine is turbo-charged or you live by the coast, 93 unleaded should be just fine.

Driving Environment

Not all cars are used for the same purpose, and most people drive on different roads. So, you should also take into consideration your specific driving environment and conditions. For more demanding driving conditions, like hilly terrain and long distance driving it’s best to use a higher octane fuel like 95 unleaded. But, if you are just driving around town or to the office each day, 93 unleaded is a great economic option.

Which is right for me?

Here is a quick flow diagram to help you choose the correct fuel for your car.

I’ve been using 93 but should be using 95 unleaded, will my engine be damaged?

First, don’t panic, this just means that your engine’s performance will have been dampened and your fuel consumption might have been higher. It’s unlikely that any serious engine damage has been done. Unless your engine has been knocking which can cause serious damage. It is best to switch over to 95 unleaded to avoid damaging your engine plus you will get better performance and improved fuel efficiency.

On the other hand, if you have been using 95 unleaded  instead of the recommended 93, you are just wasting your money. 95 unleaded won’t improve performance of your car, that only needs 93 unleaded fuel. Always check what your car manufacturer stipulates.

If you are still unsure, check your vehicle owner’s manual. We understand that your car plays an important part of your daily life, transporting you and your loved ones. Michanic is dedicated to providing the most convenient services for our customers, so if you have any other questions or concerns regarding your car, feel free to talk to our customer service team through email at [email protected], or by phone on 087 803 9000.

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