Read your owners guide!

See http://www.nissanusa.com/owning/vehicle-care/maintenance.html for
the proper maintenance schedule.
You could also look at
http://www.nissanusa.com/pdf/techpubs/2007/2007_N_SMG.pdf for the 2007
Maintenance Guide to get an idea of what is required.

These statements are from my 2006 Frontier Owners Guide:

"ENGINE COOLING SYSTEM

"The engine cooling system is filled at the factory with Genuine
NISSAN Long Life Antifreeze/Coolant to provide year-round antifreeze
and coolant protection.The anti-freeze solution contains rust and
corrosion inhibitors. Additional engine cooling system additives are
not necessary.

"Aftermarket fuel additives

"NISSAN does not recommend the use of any aftermarket fuel additives
(for example, fuel injector cleaner, octane booster, intake valve
deposit removers, etc.) which are sold commercially. Many of these
additives intended for gum, varnish or deposit removal may contain
active solvents or similar ingredients that can be harmful to the fuel
system and engine.

"Oil additives

"NISSAN does not recommend the use of oil additives. The use of an oil
additive is not necessary when the proper oil type is used and
maintenance intervals are followed."

Regards,

Ed White