Business operating costs are set to rise and household finances will come under renewed strain this month, with the price of petrol, diesel, liquefied petroleum gas and illuminating paraffin all set to rise steeply from Wednesday as the US-Iran war continues to disrupt global oil supply.The latest monthly price adjustments announced by the department of mineral & petroleum resources on Monday showed the pump price of 95-grade petrol will climb by R1.34 to R26.92/l in the economic hub of Gauteng. The wholesale cost of diesel, which unlike petrol is not regulated at the retail level, will jump by R2.95 and R3.15 for 0.05% sulphur grade and 0.005% sulphur grade, respectively, to up to R29.11/l in Gauteng.The wholesale price of illuminating paraffin, used by many South African households for lighting and cooking, will rise by R2.13/l to R20.89 in Gauteng, while gas will cost R0.69 more per kilogram at R37.39.South Africa, a net importer of crude oil and finished petroleum products, has been hit hard by the turmoil in global markets since the US war against Iran broke out in late February, playing havoc with the flow of cargo through the Strait of Hormuz.A global study by the Finland-based Centre for Research on Energy and Clean Air (CREA) lists South Africa, a net importer of crude oil and finished petroleum products, among the top 20 countries that paid the most for the price shock between March and August.It said local fuel importers have incurred at least $3.5bn (R56.48bn) in extra costs since the outbreak of the conflict created the largest and most sustained price shock since the 1990 Gulf War.Domestic fuel prices lag international movements by about a month, based on the cost of importing the products over the preceding 30 days, calculated by the state Central Energy Fund, which manages energy assets, strategic fuel reserves and related investments to secure the country’s energy supply.In the latest period under review, the average Brent crude oil price increased from $82.37 to $87.88 due to “the continued US-Iran tensions, uncertainty regarding the flow of oil through the Strait of Hormuz and higher shipping costs”, the mineral & petroleum resources department said in its statement.The average international prices of petrol, diesel and illuminating paraffin also rose due to supply shortages caused by the separate conflict between Russia and Ukraine, which has been raging since 2022.This was offset by a stronger rand on average against the dollar during the previous month, which led to lower contributions to the basic fuel price of petrol, diesel and paraffin.Read: Consumers to pay more for petrol and diesel from September 2The basic fuel price, which reflects import parity costs, global product prices and shipping-related import costs and the rand exchange rate, makes up only a portion of the total price consumers pay at the pump. The government adds other fixed and regulated costs such as the general fuel levy, carbon fuel levy and Road Accident Fund levy.The higher fuel costs point to continued strain for South African businesses for the rest of the year after confidence slumped in the second quarter under the weight of increased input costs. The Bureau for Economic Research (BER) and Rand Merchant Bank will publish the third quarter business confidence index (BCI) on Wednesday.Output in the mining and manufacturing sectors, in particular, has weakened, pointing to continued weak GDP growth in the second quarter of 2026 after the economy expanded by a subpar 0.5% in the first three months of the year.The latest fuel price adjustments will also place renewed pressure on motorists and households, the South African Petroleum Retailers Association (Sapra) said.“Fuel remains a critical input cost for households, small businesses, logistics operators, agriculture and many other sectors of the economy. An increase of this scale, particularly in diesel, will be felt well beyond the forecourt and may add further cost pressure across the value chain,” Sapra national chair Henry van der Merwe said in a statement.The latest fuel price jump also points to persistent inflation pressure — despite a likely temporary relief in July — which the South African Reserve Bank will be keeping a close eye on before its next policy meeting on September 23 and its last one for the year in November.The Bank kept its benchmark policy rate unchanged at 7% in July after raising it by 25 basis points in May but made clear it would not hesitate to act on any signs of second-round effects from the global oil price shock.Business Day