The 2.5-liter four cylinder has long been the bread-and-butter choice in the Altima line, but enthusiasts loved the muscular range-topping 3.5-liter V6 that offered up 270 horsepower. That engine is now replaced with a 2.0-liter turbo that drops horsepower to 248, but Nissan says that change also brings a boost to fuel economy. The base 2.5-liter is also up to 188 horsepower.