Here's How Often McDonald's Changes Its Frying Oil, According To Employees
Fast food restaurants can get an unsavory reputation for less-than-sanitary conditions in their kitchens. It's almost entirely unwarranted — the local health department would have shut them down long ago — but the myth persists. One area of interest is the fryers, which at McDonald's are used especially to cook the greasy, glorious fries, as well as the McNuggets (which are best eaten employee-style). You might have wondered how often the fryer oil gets changed, as stories persist that some restaurants never swap it out. However, according to a few McDonald's employees, the oil-change process happens about once a week.
"I worked in two McDonald's and the oil was changed [weekly]," one Redditor on an r/AskReddit thread reported. Another employee on a different r/AskReddit thread said they change the oil "lots," without specifying an exact time-frame, but they did mention that the machine itself has an alert system when it's time, and it goes off often enough to be annoying, especially when the restaurant is busy.
Finally, a third employee said on Reddit that their store the oil was only changed every two weeks, but by the time they got around to it, the oil was nearly black. They were then advised to change it once a week, in line with previous employee reports.
How the oil gets changed and what McDonald's does with it
To change its cooking oil, McDonald's uses an easy and straight-forward process. The old oil gets drained into what looks like a metal lock box with a cart handle attached; it gets wheeled under the fryers and the oil is released to drain into it. The fryers are far more technically advanced than you might think (certainly more than the machines in use when the original CEO betrayed the founders of McDonald's in the early 1960s). Today's McDonald's fryers have digitized controls, a filtration system that is constantly working to keep the oil cleaner, and even a feature that automatically adds a little oil when the levels get low.
@random815mcd how we change our oil. our store does this every 7 days. #McDonald #fryer #fypage
You might be wondering what happens to all that oil once it's been drained from the fryers. The answer is actually really cool: McDonald's contributes it to be turned into biodiesel fuel. Through a process called transesterification, cooking oils can be converted into both biodiesel and glycerin, at a 1:1 ratio (so 200 pounds of cooking oil becomes 200 pounds of fuel). And not just any fuel; in some cases, it is specifically turned into jet fuel. Think about that the next time you grab McDonald's in an airport.