Poor fuel quality results in life-threatening air quality
July 25, 2019
Steady increase in the cost of motoring
July 31, 2019

93 or 95 Octane – Which petrol grade is best for your vehicle?

The government is attempting to change the way 93 octane petrol is sold inland by setting a price ceiling but not a recommend selling price, as is currently the situation with diesel fuel.

Vishal PremlallVishal Premlall, Director of the South African Petroleum Retailers’ Association (SAPRA), a member of the Retail Motor Industry organisation (RMI) says this move could have unintended consequences, according to an article in Automobil, the RMI’s monthly publication.

One of these consequences could be confusion for the paying customer with differing prices for 93 petrol and diesel fuel and a fixed price for 95 petrol. Another is that the price-cutting by retailers could impact the sustainability of their businesses and possibly result in job losses.

Then one must look at the need for more expensive 95 when 93 could be sufficient.

“While 95 has a higher-octane rating than 93 octane it is not an indication of the energy content in the fuel. 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,” said Adrian Velaers, Senior Technical Advisor – Retail and Commercial Fuels, at Sasol Energy.

“The design of the engine dictates whether knock happens or not. Most road car engines will be conservatively designed and can operate on 95 octane at the coast and 93 octane inland without any knocking. Turbocharged engines, which boost the pressure in the combustion chamber, are more susceptible to knocking and could benefit from the higher-octane fuel.

“There will be a slight benefit in performance and fuel economy when using 95 octane fuel with a turbocharged engine driven close to its power limit, but again this is very dependent on engine design and driving style,” added Velaers.

Jakkie Olivier, the CEO of the RMI, cautions drivers to check manufacturer’s fuel specifications for their specific vehicle. “You don’t want to risk losing your warranty or damaging your engine by using the incorrect grade of fuel. We recommend that you consult the owner’s manual or petrol flap for the correct information.”

octane - Petrol Price of petrol in SA