FWIW, when I got my 2005 TBird I decided I would use only the best oil, not that schlock Ford stuff. I did internet research on the "Bob is the Oil Guy" website (check it out!) and was surprised to find people just gushing about the
Motorcraft semi-synthetic oil. It turns out it's excellent, as are the
Motorcraft oil filters, so I have stuck with it (although now I use mostly the
Motorcraft Full Synthetic, which some Ford dealers do carry). Most likely the
Motorcraft oil is what your Lincoln dealer is using and you will be fine with it. I have talked with many cab drivers (who mostly use Ford Crown Victorias) and they routinely get 350,000 miles out of their engines, but do change the oil every 3000 miles (city driving is what is referred to as severe duty, so 3000 is what is generally recommended, but 5000 is fine for highway driving), so your Tbird should make it to 350,000 also, with the proper maintenance it is likely to receive. The cab drivers usually are required to get rid of the cars at the 350,000 mile point by regulation, usually they are still running fine. Changing the
transmission fluid every 25,000 to 40,000 is critical if you want it to last the distance (and use
Motorcraft fluid).
I have used Mobil 1 and Amsoil Full Synthetic oils in my Jeep Cherokee and had great results - the car is still running fine at 350,000 miles with no history of any major engine or transmission problems, so they are great in my book (and in any one else's, most likely), but it is best to start out with these oils on a fairly new engine, as introducing them into older vehicles can result in the development of oil leaks (the companies may deny this, but I have run across people who have experienced this). If you do want Full Synthetic, consider
Motorcraft, as it has a type III base, which is better on the seals and may provide better corrosion protection than the bases in Mobil 1 and Amsoil. Or just stick with the
Motorcraft Semisynthetic - you will be fine (check out the info on the "Bob is the Oil Guy" website if you would like more reassurance about this.