You can put in the more free flowing GN4 (10w30) and see if that alleviates the perceived tick you are hearing. As I mentioned earlier, I'm running 5w40 Rotella, not 15w40.
I meant to say that you should stay with a synthetic since that oil's properties exceed dino oil for longevity; such as shear life and contaminant suspension.
I'm also not 100% sure it's not an injector I hear ticking. I'll change it in the next couple weeks and report back.
2013 F6B 1800B Don't be a thermometer, be a thermostat