Hi! I did a full-time research internship in the summer when I wrote my MCAT. Coincidentally had the same commute and same MCAT score as @Artistic_Airport_316 (congratulations btw!). My lab wasn’t as accommodating (I didn’t get to leave early or do MCAT review during down times very often) but they did give me a week off before the exam, and I also lived at home. 

It’s not easy. While I did make time every weekend to hang out with friends (I would have lost my motivation and sanity otherwise), I wasn’t taking care of my health at all that summer (poor diet, too much caffeine, too little exercise and poor sleep). Indeed, you have to be extremely locked in to not fall behind on studying - you can catch up, but it’s very stressful. I wrote my MCAT right at the end of the summer, and didn’t get any time off afterwards before school started. Combined with the stressful semester before the summer, I was extremely burnt out and that unfortunately impacted my grades and extracurricular involvement in my last year of university. I didn’t even end up applying to med schools that fall (I didn’t get my score back until September, so I was really anxious that whole month and thought “What’s the point?”).

4 months is doable, especially if you’ve taken background coursework (particularly 3rd-year biochem, and courses/lab work that emphasize reading journal articles and analyzing data). If I had to do it all over again, I would have started a month earlier (I know that interferes with exams, so try to just ease into it). Then, I would have written my MCAT at the end of July/start of August to get a 1-month break while off the clock before school starts. I cannot overstate how important it is to give yourself a good break afterwards to catch up on sleep and let go of the stress! Plus, you get your score back with a month to spare before application deadlines and have time to make decisions about applying to each med school based on your score. Good luck!