Remember, Amsoil signature series changed every 3k with bypass filtration. Make sure it is 0w30 for those cold Florida starts. It helps me sleep at night because it is cheap insurance.
Sorry to go off the rails, couldn't resist but littleblazer said that word that gets my blood pressure up.
On this note, Amsoil does make a top notch product but like Mobil, it is not worth the price. You can greatly extend your oil change indexes with conventional group 2 and 3 oils by using a quality filter and used oil analysis.
Engines, while in some ways have been cheapened by the bean counters, they are light years ahead of what they were 20 years ago. Today you can pull apart a modern, high mileage engine and still see the cross hatch in the cylinders. They don't wear out the same way the old ones did. The seals are made much, much better than they ever were. If a seal is leaking, its usually because its defective, not worn out. High mileage oil wont fix that.
Also, don't be so concerned with brand. There are only a few oil companies making engine oil. Mobil made oils under the ACDelco and Supertech labels. Warren is relabeled as various others as well as Supertech, depending on what region of the country you are in. Citgo currently makes most of the Canadian Tire brand, Motomaster oils. Imperial Oil, then Shell made Motomaster previously. SOPUS (Shell) makes Pennzoil and Quaker State flavors. Most are nearly identical in blend. PetroCanada has made ACDelco. Supertech and now Tune it in Canada appears to be made by Safety Kleen.
All of these oils are just fine. Find the grade, API index and pick your price point. In a standard change index and outside very harsh conditions, you will never see any difference in engine wear from group 2 conventional and Amsoil SS. Don't believe me? Try to standardize your driving habits and do used oil analysis.