Hey Rio!

I'm not in Mechanical Engineering but I've got some friends in Engineering, and one in Mech specifically...

That workload sounds about what he experiences... apparently (at least at my university) Aerospace Engineering is more time consuming...

I've heard of the 3 hours of studying per one hour of lecture... it's what is generally expected of all students. Just from my experience and from what I've seen, if you spare a few hours here and there to study the stuff you don't understand (or lessen the amount of time spent on material you truly understand) ... you should be "fine" with 15 hours of studying per week. Just realize you're not Superman, and it is quite possible to fall behind - especially during exams or essays/assignment due date periods.

Hope that helps and good luck!