Karen 
2004 Nissan Frontier Crew Cab 4dr Crew Cab XE-V6 4WD LB (3.3L 6cyl 5M)
Great Year for the Nissan Frontier:  2004
 You won't get 50 mpg with this truck.  It is, after all, a truck.  I got 14-15 mpg combined gas mile p/gallon with a fully loaded bed (1000 lbs.)!!!  (a homemade camper lives on the bed).  Otherwise, about 18-20 mpg.  I bought this truck used about 4 years ago.  It is 12-years-old now.  I put in a new battery, and a set of great tires.  I do the scheduled maintenance.  That's it!  It always starts, always runs.  No issues.  Reliable.  Solid.Update:  Camper, having served its function ("home" whilst moving and building a new house on raw land), has been removed.  Gas mileage:  20-22 in zero traffic--mostly highway--miles.  Climbs my very steep drive in 4WD like a goat.  Black Bart, for so he is named, is 14-years-old now.  Still Starts.  Runs.  A few cosmetic things that I might fix in future--inside and out--but nothing mechanical.  Oh, I forgot to mention in my first review:  I installed a "super cooler" on my radiator for the cross-country trip whilst carrying the camper, and see no reason to remove it!   I doubt I will ever sell or trade this truck, as it suits my budget and transportation needs up here in the Appalachian Mountains 'to a T'!