2013 Taurus with 33,000 miles. I have been using the Ford branded synthetic blend oil since purchased. I’d like to switch over to full synthetic oil. I’ve had some unfortunate issues using full synthetic on other make cars in the past. These cars had low mileage and each was relatively new at the oil change. Both vehicles developed leaks within days of the change and both occurred at the valve covers. So, my experience with synthetic has not been good. My question is has anyone here switched over to full synthetic after a significant amount of miles? Any issues? I understand tolerances today are much different than they where years ago and this shouldn’t be a consideration. Opinions? Thanks in advance!