Maxlife can help with leaks and it does protect engine internals better. But it is also manufactured to the thicker side of the given viscosity, which can affect your MPG. I didn't have any leaks but I used it for about 30,000 miles then used Napa HM for 10,000 miles. I noticed my truck was a bit sluggish on HM oil. My truck runs a bit faster and my MPG went up a couple miles too when I switched back to Napa conventional 10W30.
Maxlife is a great oil but there are trade-offs in gas mileage and performance. It is also not rated energy conserving by the API.