Why is diesel more expensive than petrol in South Africa?

Petrol prices go up. Diesel goes up even more. Then petrol comes down while diesel heads in the opposite direction.

If you've been watching South Africa's fuel prices lately, you may be wondering why diesel can cost more than petrol – and why the two don't always move together.

In September 2026, that difference was difficult to miss. Petrol increased by R1.29 per litre, while diesel increased by between R2.939 and R3.149 per litre, depending on the grade.

So, what's going on?

The short answer is that petrol and diesel are different refined petroleum products with different international supply-and-demand pressures. South Africa also regulates their retail prices differently. Add international fuel prices, the rand/dollar exchange rate, transport costs, taxes and levies into the mix, and diesel and petrol can move very differently from one month to the next.

Let's break it down.

Diesel can become more expensive than petrol when international diesel prices rise faster than international petrol prices.

That's important because South Africa's fuel-price calculations aren't based only on the price of crude oil.

According to the Department of Mineral and Petroleum Resources, the Basic Fuel Price reflects international refined petroleum product prices and import-related costs, converted into rand.

Petrol and diesel also have different international reference markets.

That means a shortage or surge in demand affecting diesel doesn't necessarily have the same effect on petrol.

September provided a particularly clear example.

The DMPR's September 2026 fuel-price announcement confirmed increases of R1.29 per litre for both grades of petrol.

Diesel increased considerably more:

• 0.05% sulphur diesel increased by R2.939 per litre.
• 0.005% sulphur diesel increased by R3.149 per litre.

Interestingly, the rand strengthened on average from R16.46 to R16.26 against the US dollar during the review period. According to the DMPR, that actually reduced pressure on the Basic Fuel Price.

In other words, the exchange rate provided some relief – but it wasn't enough to cancel out the other pressures affecting fuel prices.

Think about where diesel is used.

It's not just powering diesel passenger cars.

Diesel is critical to trucks and freight, agriculture, mining, construction, generators and many other commercial and industrial activities.

That gives diesel a different global demand profile from petrol, which is more closely associated with passenger vehicles.

When international diesel supply tightens or demand increases, the price of diesel can therefore rise faster than petrol.

And South Africa isn't isolated from those movements.

Because our Basic Fuel Price uses international refined petroleum product prices as part of its calculation, what's happening thousands of kilometres away can eventually make itself felt at your local filling station.

Yes – but only partly.

This is one of the biggest misconceptions about petrol and diesel prices.

Crude oil is the raw material used to produce petroleum products. But motorists don't put crude oil into their cars. They buy refined petrol or diesel.

South Africa's Basic Fuel Price therefore considers international refined product prices rather than simply copying the Brent crude oil price.

Global crude oil prices still matter, but so do refinery capacity, international product demand, shipping costs, supply disruptions and the availability of particular fuels.

That's why seeing an oil-price decrease in the news doesn't automatically mean diesel or petrol will fall by exactly the same amount.

Because they're different products facing different market conditions.

South Africans saw a good example in August 2026.

Petrol decreased by 52 cents per litre while wholesale diesel increased by between R1.23 and R1.38 per litre.

It may look strange at the filling station, but it makes more sense once you understand that international petrol and diesel prices don't have to move together.

If international petrol prices weaken while international diesel prices strengthen, South Africa's monthly adjustment can reflect both movements at the same time.

So, yes petrol can get cheaper while diesel gets more expensive.

The rand has a big part to play because international petroleum products are priced in US dollars.

When the rand weakens against the dollar, South Africa needs more rand to buy the same dollar-priced fuel.

That can place upward pressure on both petrol and diesel prices.

A stronger rand can provide some relief.

But there's an important catch: the exchange rate is only one part of the calculation.

A stronger rand doesn't guarantee cheaper fuel if international petroleum product prices are rising strongly at the same time.

Yes, and this is something many motorists don't realise.

South Africa's petrol retail pump price is regulated. The official price therefore determines what motorists pay for petrol within the relevant pricing zone.

Diesel works differently.

According to the DMPR's fuel-price structure, the retail price of diesel is not regulated. Instead, an official wholesale list price is published.

Retailers can then determine their retail diesel margins.

That's why you may see different diesel pump prices at filling stations, while regulated petrol prices within the same pricing zone are generally the same.

It's also important when comparing petrol and diesel prices online: an official diesel figure may be a wholesale reference price, while the petrol figure is a retail pump price.

They aren't always a like-for-like comparison.

The Basic Fuel Price, usually shortened to BFP, is one of the most important parts of South Africa's fuel-price calculation.

In simple terms, it estimates the market-related cost of importing refined petroleum products into South Africa.

It takes factors such as international product prices, shipping-related costs and the rand/US dollar exchange rate into account.

Domestic components are then added, including applicable taxes and levies, transport costs, margins and regulated charges.

That's why the price at the pump isn't determined by one number.

It's the result of several international and domestic costs coming together.

Where you fill up also matters.

South Africa uses geographical pricing zones, and transport costs form part of the domestic fuel-price structure.

Fuel supplied to inland areas has additional transport costs compared with fuel supplied closer to the coast.

This helps explain why motorists in Gauteng may pay more than motorists at the coast.

No. Diesel being more expensive today doesn't mean it will always stay that way.

International petrol and diesel markets are constantly changing, along with crude oil prices, the exchange rate and domestic fuel-price components.

There will be periods when diesel is more expensive and others when the relationship changes.

Instead of asking whether diesel is always more expensive, it's more useful to ask:

What's putting pressure on diesel prices right now?

That gives you a much better picture of what's happening at the pump.

That's a different question – and the answer depends on how you use your vehicle.

Diesel vehicles can offer good fuel economy, particularly for drivers covering longer distances, but fuel consumption isn't the only cost to consider.

Think about your total cost of ownership, including servicing, maintenance, tyres, finance, fuel and car insurance.

If you're choosing between petrol and diesel, look at how many kilometres you actually drive, the vehicle's real-world fuel consumption and the difference in purchase and running costs.

A cheaper litre of fuel doesn't automatically mean a cheaper car to own – and an expensive litre doesn't automatically make a vehicle uneconomical.

You can't control global petroleum markets, but there are a few things you can control.

Correct tyre pressure, regular servicing, smooth acceleration, reducing unnecessary weight and planning trips more efficiently can help improve fuel consumption.

For more practical ideas, read our guide to car maintenance tips that can help you save money when petrol and diesel prices rise.

You can also read our fuel-efficient driving tips to find simple ways to get more from each tank.

If you're trying to understand where South African fuel prices could be heading, don't watch the oil price alone.

Keep an eye on:

• International petrol and diesel product prices.
• Brent crude oil prices.
• The rand/US dollar exchange rate.
• Global diesel supply and demand.
• Refinery and shipping disruptions.
• Changes to South African taxes and levies.
• Official monthly fuel-price announcements.

The DMPR publishes South Africa's official fuel-price updates, making it a useful source when the next monthly adjustment is announced.

Whether you drive petrol or diesel, fuel is only one part of keeping your vehicle on the road.

Maintenance, repairs, tyres and car insurance all contribute to your monthly motoring costs, which makes it worth reviewing the bigger picture when household budgets are under pressure.

While you can't control what happens to global fuel prices, you can make informed choices about how you drive, maintain and protect your vehicle.

Looking at your overall motoring budget? Get a Miway car insurance quote and find cover that suits your needs.