Synthetic In High Mile Engine?

82k isn't exactly high mileage, so if the motor's in good shape (not sludged, burning oil or similar) I'd go right ahead. I think the 15w50 is a bit on the heavy side, tho.

On a high miler, or engine with an unknown service history or possibly suspect due to noise, smoke, whatever, I'd run an Arx treatment or flush to try and clean it up first:

http://www.auto-rx.com/

I don't recommend the solvent-type quick flushes. AutoRx is best, but pricey.