What's Reefer Oil Change

Reefer oil change, what is that?

I googled the word "reefer", as turn out it's a slang word for drug of some sort according the urban dictionary.

What I had in mind was about the preventative maintenance program (PM) offered at may truck stop/commercial vehicles. In this case "Reefer" refers to the refrigerated container, or shipping trailers equipped with refrigeration system.

The refrigeration trailer/container uses combustion engine to generate the power to run the refrigeration system. It also requires the PM like tractor and trailer.