File picture: Timothy Bernard / Independent Media.

Johannesburg - The price gap between 93 Unleaded and 95 Unleaded petrol will more than double from Wednesday, October 2, according to figures released by the Central Energy Fund over the weekend.

While the price of 95 Unleaded is set to increase by 18 cents a litre, 93 Unleaded will in fact become 4 cents cheaper. Whereas 93 ULP currently costs 20 cents less than 95 ULP, from October 2 the lower octane fuel will save you 42 cents a litre at the pumps (at R15.79 a liter versus R16.21 in Gauteng) and that's nothing to be sniffed at.  

In fact if you have a 50 litre fuel tank, then 93 ULP will save you R21 for every refuel, which could add up to over R1000 a year if you fill up once a week.

Keep in mind though that the lower octane 93 ULP is only available in the inland regions of South Africa, although coastal motorists do at least pay less for 95 ULP due to lesser transport costs.

But should you fill your car with 93 Unleaded?

Many motorists believe that 95 ULP 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.

So how does octane affect performance and reliability?

Adrian Velaers, a senior tech advisor at Sasol, says 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. Do not switch from 95 ULP to 93 ULP without at least checking this to be safe.

IOL Motoring