(Updates with company comment in second paragraph.)

Feb. 2 (Bloomberg) -- Sasol Ltd. said earnings in the first half through December probably rose as much as 90 percent from a year earlier as the biggest maker of motor fuel from coal benefited from higher oil prices and a weaker rand.

“The expected increase in earnings was mainly due to solid operational performance in our businesses, coupled with a strong improvement in the average crude oil and product prices and a weaker rand-dollar exchange rate,” the Johannesburg-based company said in a statement today.

Sasol, with operations in countries including Mozambique, Qatar, Iran and the U.S., earned about two-thirds of its operating profit from its South African energy business in the 2011 financial year. Crude oil was an average 14 percent higher at $91.81 a barrel in the six months ending December, compared with $80.60 a year earlier.

The rand depreciated 16 percent against the dollar in the same time, making it the world’s third-worst performer after Hungary’s forint and Poland’s zloty, according to data compiled by Bloomberg. It traded at an average of 7.6227 per dollar in the period, 6.7 percent weaker than the average of 7.1137 rand a year earlier.

The company also benefited from gains on foreign-exchange contracts, it said. Its shares rose to the strongest level in more than a week, trading 1.1 percent up at 407.02 rand at 2:04 p.m. in Johannesburg.

--Editors: Ana Monteiro, Amanda Jordan

To contact the reporter on this story: Jana Marais in Johannesburg at jmarais@bloomberg.net

To contact the editor responsible for this story: John Viljoen at jviljoen@bloomberg.net