An old nuclear engineer (a real one) I know out near Philly ran Amsoil in his Stealth Twin Turbo and actually sent his used oil to 2 different labs for analysis after 3 different oil changes (5k, 10k, and one 15k). He was using Amsoil oil filters as well. The results showed that he was basically pissing money away changing it earlier than 15k and last I knew he was going to try 25k mile oil. The drop off in protection between 5k and 15k was, according to him, almost non-existent with Amsoil full synthetic.
I’m not at all criticizing you for changing it at 5k, but as much as Amsoil products cost, you might think about sending the oil to a lab (I think he said it actually cost him about the same as a single oil + filter change) to see where you’re at. The results might save you a good bit of money in the long run.