I have used full synthetic oil (Mobil-1) in my last 4 new vehicles with excellent results. I had a 2001 Sport Trac and changed to synthetic oil at 10K miles. I had a 2003 Saturn Ion and used synthetic oil in that from the first oil change, again I had excellent results.
I traded in my 2001 Sport Trac for a new 2003 Sport Trac and switched to syntheitc oil at the first oil change. and finally, I just bought a new 2008 Mercedes Benz which comes from the factory with Mobil-1 synthetic oil and only requires oil changes, 1 per year or every 13K miles If it';s good enough for Mercedes Benz, it should be good enough for Ford, Chevy or any other brand of vehicle.
If you do go with synthetic oil with the extended oil change intervals, you need to buy a quality filter that will work for the full extended change interval.
If you change the oil every 10K-15K miles you doj not have to add any additional additives to the oil.
Royal Purple and Amsol make excellent products, however for a daily driver vehicle I don't think the added cost and inconvenience finding those products are necessary.
A goo quality synthetic oil that you can easily purchase almost anywhere, and one that is available at the local lube or service centers is a better choice. I chose Mobil-1 for that reason and I think Mercedes Benz making the same choice confirms that it must be an excellent quality synthetic oil.
If you buy some exotic oil you may find it difficult to find which may delay your oil change and they probably are not any better for 10K-15K miles of use than any over the counter synthetic oils available anywhere.
...Rich
