Shortlly after trading opened on Monday, the fuel giant Sasol lost almost half of its share price.
Sasol stocks started trading at R102.48 in the morning but fell to R79.00 immediately.
American banking group Goldman Sachs warns that oil prices could fall as low as $20 a barrel.
Sasol produces fuel from South African coal and natural gas from Mozambique, but its fuel is sold at prices based on international oil prices in dollars and the rand-dollar exchange rate.
So its earnings are closely linked to the dollar price of oil.
Sasol also went public on Friday after Moody’s Investors Service downgraded it to junk status.
Its long-term debt rating has been downgraded by one level from Baa3 to Ba1 and is now below investment grade.