I've been at my current university for 3 and a half years. I applied out of undergrad to a PhD program, but my advisor suggested I defend a masters before launching into the PhD just in case. I did last year. Research for the masters took longer than expected so I was done with PhD coursework before even beginning research. To fill the free class time I had my advisor suggested I take business classes (I want to end up in industry) and I eventually convinced him to let me do an MBA during the slow start of PhD research.

Fast forward to this year and I'm doing the MBA full time and PhD work is almost non-existent.

I like the business side of things and for the first time realize I could be happy not doing primary research the rest of my life. I'm currently debating whether staying to finish the PhD is important to me, but I'm not sure whether these feelings are due to my not currently being active in the lab.

If I was providing some value to my advisor I wouldn't feel terrible about letting him fund the rest of my MBA and then leaving. He wouldn't get the amount of work out of me that he would if I stayed for the whole PhD, but he would get something. If I wasn't using grant money I would probably stay until at least summer, get back into the swing of lab and see how I felt, but I am using grant money and I'm not sure thats an ok thing to do.

Do I have an ethical obligation to let my advisor know I might want to leave? Is letting him know going to absolutely shut doors for me?