Mahantesh Sabarad, senior vice president at Fortune Equity Brokers, said Maruti's net profit jumped 80 per cent in the fourth quarter on account of the merger of its engine subsidiary, a depreciation in the yen, large other income and an unusually low tax rate of 16 per cent. "Of these, three aren't sustainable," he said, adding that only the yen depreciation and margin performance seem sustainable in the upcoming quarters.