File picture: Courtney Africa / Independent Media.

Johannesburg - While 95 Unleaded is the only option for South African motorists living at the coast, those residing in the inland regions can choose between that and the slightly cheaper 93 Unleaded.

However, many motorists believe that 95 Unleaded is essential for avoiding long term engine wear and tear as well as extracting the best performance and economy out of their car.

But experts argue that this is actually unnecessary in the majority of cases, not to mention the fact that you could also be wasting your money.

Let’s take a quick look at the cost differences

According to May 2019 forecourt prices, a litre of 93 Unleaded costs R16.48 in Gauteng, versus R16.67 for 95 ULP. 

That extra 19 cents a litre can add up to R9.50 for a full 50 litre tank, and if you’re filling up once a week then it’s a price difference of about R500 per year. 

Tempting?

But how does octane affect performance and reliability?

Adrian Velaers, a senior tech advisor at Sasol, explains that contrary to popular belief, octane is not an indication of energy content.

“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,” Velaers states.

But don’t turbo engines require 95?

While it’s true that turbochargers boost the air pressure entering the combustion chamber, making the engine more susceptible to knock, it really depends on the engine in question and what the manufacturer recommends.

However, generally speaking, 95 petrol will only give you a performance and economy advantage when you're driving extremely hard - and naturally, that efficiency advantage is more than cancelled out by the hard driving. 

Here's the bottom line

“For non-turbocharged engines there is no benefit, 93 is essentially the same fuel just cheaper," Velaers explains.

"For turbocharged cars driven conservatively, there will also be no benefit to using 95 petrol instead of 93. 

"But if you care about maximum performance from your turbocharged car, or the manufacturer specifically requires it, then you should pay more and use 95”.

Switching between 93 and 95 is also not a problem, as the engine simply adapts its spark timing if driven close to the knock limit.

Always double check the fuel flap

However, Jakkie Olivier, CEO of the Retail Motor Industry Organisation cautions that motorists considering switching octanes should double check what the car manufacturer stipulates.

“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.”

The stipulated octane can usually be found printed on the inside of the fuel flap, and should also be mentioned in the owner’s manual.

IOL Motoring