Should you be putting 95 or 93 Octane petrol in your car?

There is much debate around whether 95 Octane petrol is an essential to get the best performance out of your car and to avoid unnecessary wear and tear. “This is a question that often pops up in the industry,” says Jakkie Olivier, CEO of the Retail Motor Industry Organisation (RMI).


Towards the end of last year there was also an attempt by Government to bring about change to the existing dispensation on 93 Octane in the inland region. The proposal included not setting the retail price of 93-Octane petrol anymore but rather having a price ceiling put in place for the fuel. It said the move will create competition, which will lower the price. The department believes people are unnecessarily using 95-unleaded petrol.


Vishal Premlall, Director of the South African Petroleum Retailers Association (SAPRA), a proud association of the RMI, raises the unintended consequences of placing a price cap on 93 Octane in South Africa. “We believe there will be micro-economic concerns and it will create confusion for the paying consumer. For one the perceived price relief for consumers applies to inland consumers only. There will be no benefit for coastal consumers. Along with that, forecourts will have differing prices for 93 Octane, differing prices for Diesel and a set-price for 95.”


He adds that for retailers the proposed changes will impact business sustainability possibly resulting in job losses. “There’s also a good chance that the uncertainty will affect investor confidence and the security of supply in some areas.”


With discussions still taking place around the proposal, should consumers be more informed about what petrol they are putting into their vehicles?


Adrian Velaers, Senior Technical Advisor – Retail and Commercial Fuels Sasol Energy, explains that while 95 has a higher-octane value than 93, octane is not an indication of the energy content in the fuel, and this is where the myth comes in that 95 is better than 93. “Octane is merely a measure of the fuel’s resistance to ‘knock’, a phenomenon in a petrol engine where the fuel ignites in an uncontrolled manner. Whether knock happens or not is dependent on the engine design, and most road cars will be conservatively designed and comfortably operate on 95 at the coast, and 93 in the inland without knock taking place,” he says. Engines fitted with turbochargers, however, will boost the air pressure and make the engine more susceptible to knock and could use the extra octane.


For high performance turbocharged engines being driven close to the power limit, 95 will offer a small performance advantage and lower fuel consumption. The magnitude of this is very dependent on engine design and driving style. “For non-turbocharged engines there is no benefit, 93 is essentially the same fuel just cheaper. For turbocharged cars driven conservatively, there will also be no benefit to using 95 petrol instead of 93. If you care about maximum performance from your turbocharged car, or the manufacturer specifically requires it, then you should pay more and use 95,” says Velaers.


He adds that if you are planning a trip to the coast 93 Octane is not currently available so you will have no choice. “I would recommend that if you have a turbocharged car you may want to consider filling with 95 before your trip to the coast, however there is no risk of engine damage if you don’t. You can switch between 93 and 95 and vice versa very easily as the engine will simply adapt its spark timing if driven close to the knock limit depending on which fuel or blend thereof is in the tank.

The two octane number difference between 93 and 95 actually results in a very small difference anyway, and the fuel itself is largely the same, it is still petrol,” concludes Velaers.


Olivier cautions drivers considering switching octanes to check what the manufacturer specifications are. “The most important thing to remember is that you don’t want to risk losing your warranty or damaging your vehicle by using the incorrect fuel. What you need to bear in mind is that it varies from manufacturer to manufacturer whether the warranty is affected by the owner’s fuel choice. What we recommend is that you consult the owner’s manual or petrol flap,” he says.