Got mine w/7200 on the clock. I will be using Castrol Syntec at the next oil change. I've been running it in the Lightning for years and am very happy with the performance & the price point.
My aim is to use it in the entire drive line.
My main reason for using synrthetics (Castrol in particular) is that since I started using it in the truck, when oil comes out, it looks way cleaner than the dino oil I used for the break in period.
I do not advocate using synthetics to break in a new engine, reason being that the seals & gaskets need time to absorb oil and swell slightly to do thier jobs properly. Synthetics are by and large thinner than dino oil and can migrate past the seals if they haven't swelled sufficiently during break in. This is somrthing I have seen in building and maintaining race engines (after I retired, I owned a speed shop for a time).
Whether you agree or disagree, this is my experience, and I am aim to use it to my best advantage.