Your Best Friend Just Went into Business and Opened a Fried

Your best friend just went into business and opened a fried doughnut take-out restaurant, and as a result of the type of operation, she is spending too much money on frying fat for her industrial-size fryer. In addition, once in awhile, her doughnuts are just too greasy and she does not know why. Using your food science knowledge, provide her with some advice to help make the best of her oil usage.