Sasol reduced its production guidance for its Secunda coal-to-oil plant because maintenance was taking longer than expected, it said in its September quarter update on Thursday morning.

But thanks to improved performance at its Natref refinery, Sasol said it was still on track to achieve its sales target of about 58-million barrels of fuel in its 2019 financial year, which ends in June.

In its 2018 financial results, Sasol reported Secunda's synfuel production fell 3% to 7.6-million tonnes. The drop was blamed on Eskom outages.

In Thursday's update, Sasol said it had lowered expectations that Secunda would pick up production in the financial year under way, now expecting it to only match the prior year's 7.6-million tonnes.

"The planned full shutdown at our Sasol Secunda Operations (SSO) West factory was longer than estimated mainly due to technical issues with the Steam Header 2 project and challenges with startup, which further delayed the commissioning date," the chemicals group said.

"Mining will achieve the targeted production levels of 40-million tonnes for the full year. At our Mozambican upstream operations, we delivered a robust production performance, in line with expectations."

Its gas joint-venture in Mozambique is expected to meet its target of between 114-billion and 118-billion standard cubic feet for its 2019 financial year.

Sasol said it benefited from higher Brent crude oil and product prices during the quarter and a weaker average rand exchange rate against major currencies.