Is having a completely free weekday useful for engineering students?

Yes. A weekday without classes can be useful for engineering students because it provides a block of time for laboratory or practical-course preparation, assignments, review, and rest. However, it does not automatically make the workload easier: engineering courses may concentrate laboratories and practical sessions on other days, and some work may be required outside class. The feasibility and value of such a day depend on the university, department, and year of study.