We have both a 2003 V8 and 2005 V8 in the family. I have the 2003 V8 and my parents have the 2005 V8. The 2005 V8 has a more pep accelerating off the line and more power at higher speeds. Just to tell you the difference, the 2005 V8 has 270hp, 330 ft lbs of torqye, and VVTI and the 2003 V8 has 235 hp, 320 ft lbs of torque, and no VVTI. In my opinion, I would not spend the extra money to upgrade to a 2005 just for the new engine. I am very satisfied with the 2003 V8 and the way it performs. On the gas mileage, the 2005 is still too new to give an accurate reading. It is hovering around 14-15, but the truck has not even been broken in yet. The 2003 V8 gets anywhere from 13-14 in the city and 16-18 on the highway.