[user5994461]

Not all refactoring fit neatly alongside existing work... because every refactoring fits nearty alongside the new work.

In your example, you don't refactor for fun, you refactor to integrate new things. Integrate the refactoring as part of the new work.

Guess what. The mechanic too has to deal with the old wheels, and don't get him started on the old screws that broke and the assembly that had to be cleaned just to work in decent conditions.