Is it ok to use regular fuel in a 2002 lincoln v-8 engine?

Your LS, like my 2000, likely calls for 91....AT SEA LEVEL.......for every thousand feet of elevation, you can drop one full point. So, at my 3,700 foot elevation, my LS runs fine on 87....... Taking this a step further, if you factor in temperature, barometric pressure, and humidity to arrive at "density altitude" which is what you would use to determine jetting for a carbed vehicle......My density altitude is usually between 4,000-4,500 feet. In my locale, no retailer even carries 91 octane gasoline anyhow.....90 is tops here.