In a statement, the association said it expects the price of fuel to rise by 55 cents a litre and diesel by 39 cents for May, with illuminating paraffin projected to be 41 cents a litre dearer.
"The loss of confidence by investors, and the sovereign ratings downgrades by ratings agencies Fitch and S&P, have led to the Rand slipping heavily against the US dollar, down from around R12.35 at the beginning of the month to its current position of around R13.40," the association said.
It however stated that the impact of downgrade has not yet been felt by the economy fully, and that the forecasted upswing could change in due course.
"If the Rand had stayed on its previous upward course against the US dollar, it may have been strong enough to overcome the significant increases in international petroleum prices, resulting in a smaller increase in May," statement continued.
Earlier today the national currency was trading at R13.39 against the greenback with Brent Crude Oil at $54.93 a barrel.