This is a topic that has been discussed often, and at length on LS. Do a search and you can read for a couple of hours of comments.
I have posted often on these kinds of threads, and said pretty much the same thing. Lest I repeat myself again, here a link to one of the last,
http://www.lawnsite.com/showpost.php?p=3385883&postcount=5
Not quite all the details fit, but enough for you to understand my position on the topic.
I don't know the direction of your 40 minute drive, but we might be close, or we could be pretty far apart. Nevertheless, I understand your concerns about April/May times. Depending upon the year, September/October can be hectic as well. Also, leaf removal work can make for very tough times, especially when the time changes. Your time late in the day is extremely limited.
I would say that your friends who have "an extra four hours" are not taking advantage of their time in school very well. Again, you can do a search of the topic and my postings, so will only comment here briefly. Please avoid the mentality that college is only about taking courses, grinding through the academics, and leaving school with a diploma. To ONLY view college in this way, you are cheating yourself from the other rich experiences available. No, I am not referring to heavy drinking parties or other irresponsible behaviors. Rather, I speak about organizations, clubs, and other gatherings where you can learn to work with others, develop organizational and leadership skills, and gain a large network of colleagues. Just going to classes, running home to jump on your mower, does not help foster these attributes which will be VERY important after your graduate.
I worked in mechanical engineering and related fields for decades, hired and managed engineers at all levels (associates to Phd), so I have some understanding of the stripe of worker. Anybody hiring a fresh-out-of-school engineer is looking for something to differentiate one from another. The one with greater skills OUTSIDE the pure academics will get the nod every time, if two candidates are on the same level academic wise. Finding employment is not easy these days, and the one who has a diverse set of experiences will be viewed differently.
To the contrary of my point, if you have demonstrated your ability to start and successfully operate a business, you have established a point of differentiation as well. How important this might be, over against some of the things mentioned above, will depend upon the potential employer.
Having said all that, I'm not sure of your longer-term goals. Starting your own business as a new graduate with a BS in Engineering is very unlikely. You may have aspirations for graduate school. Most of my comments are directed toward the typical string of events -- graduate, and get employment with an established engineering firm, or division.
You clearly are not intending to make grass cutting your career. Good!!!!! If you think you have extra time while attending Pitt, my suggestion would be to find part time work doing flunky work within an engineering context. This might be in a consulting firm, in a public setting, in a larger corporation with an engineering department, etc. Even if you only have 10 hours of work per week, this experience is very critical.
Further, the time off in the Summer, April 15 to August 15, you have much time to work full-time for an engineering firm, division, or similar. Again, this experience is VERY IMPORTANT, far more important that mowing some lawns. This experience will give you a couple of things:
1. Insight into what happens in the engineering discipline. Maybe after seeing what mechanical engineers do, how they think, what kind of people they are to work with, and so forth, you may decide, "This is not for me!" This is important to know before investing large amounts of time and money into a field you may not like.
2. You establish connections within the field. It may be the connections within the company, or those outside (e.g. professional organizations, ASME for example). These connections will be critical in finding full-time employment later. Networking is the primary way to find work.
3. You make yourself known to others, and get to know yourself in a working environment. Others will know your skills, and you will get to know better what challenges you, what is of interest, and what you dislike. These working experiences often are the best way of finding out about yourself, in ways not offered previously.
I hope this helps. My intent is not to be critical, but give you a viewpoint that will help you evaluate what is before you, perhaps in ways not considered. If this is all "old ground," fine, pass over it. No offense taken. If you think we are nearby, and you wish to meet to discuss, I would be happy to do so.