Octane for a 3.2 V6

I have recently started driving a super-low mileage '99 Concorde with the 3.2 liter V6. (22k miles, been in the family since new)

Can I get away with 87 octane regular fuel, or will I definitely get better power and mileage with 91 octane premium?

For this car, is it worth the 14% extra cost to use premium?

Thank you.

There should be a sticker on the inside of the fuel filler door saying what type of fuel is recommended (Or the Owners Manual is still with the car), but I believe 89 octane midgrade is recommended, you can use 87 but if you hear any preignition happening (detonation, spark knocking, etc) I would go back to the recommended fuel.