Motor oil?

weight depends on climate/usage. I only run synthtic oil because it doesn't break down like conventional. It also doesn't thicken when the temp drops

High mileage oil is just regular oil with a few anti-wear and seal conditioner additives. It's open for debate as to whether it does the same job as those additives added seperately. I personally think it's 90% marketing BS. The best thing you can do for your high-mileage engine is to change the oil regularly.

As for the weight, you should trust Ford and run 5W20 in your car. There's a graph in the owner's manual showing the recommended weights for various temperatures, and if I recall correctly 5W20 is suitable for most of the country. Yeah, it's thin oil, but the 3.8 was designed for it (even though it's an old design). Most cars sold recently have engines that have been designed for the thinner oil since it reduces windage and friction losses and saves fuel.