Even though it's a bit shorter overall than many of the other mid-size sedans, the 2008 Kia Optima has one of the roomiest cabins in its segment, with good backseat legroom and headroom. The big 14.8-cubic-foot trunk has a wide opening, too.
Car and Driver reports that the Kia Optima has a "roomy interior...stuffed with people, the Kia proved spacious and well planned." Seats are inviting: "posteriors in front sink into buckets with a cushy top layer akin to a pillow-top mattress"; however, this source notes "side support is wanting." This is also the impression at ConsumerGuide, which says that the 2008 Kia Optima's "seats are comfortable, but they offer little lateral support in turns." Nonetheless, their reviewers report "sufficient legroom and adequate headroom for tall drivers" in the front. Those in the back don't fare as well; while there is "adequate room and comfort for two adults in the back seat," beware that "knee space grows tight if the front seats are far back" and "mediocre headroom is diminished further by the sunroof housing." Edmunds also observes that while "the Kia Optima's cabin is spacious," in the back, "seat bottoms are a little short, offering less support for long-limbed occupants than many rivals' accommodations."
The 2008 Kia Optima does better in terms of storage space. Edmunds reports that "trunk capacity is 14.8 cubic feet, and all Kia Optimas have a 60/40-split-folding rear seat." ConsumerGuide opines that the Kia "Optima's decent-size trunk has hinges that don't intrude into cargo space," adding that there's "sufficient cabin storage with an ample glovebox, door map pockets, and an armrest console."
Edmunds reports that the 2008 Kia Optima's "interior materials as a whole give an impression of quality...[countering] any lack of character with a no-brainer control layout and very good interior materials." Kelley Blue Book is in agreement: "Even in base LX form, the Optima's interior materials rate well above merely acceptable. ...on those cars with leather we were impressed by the leather's tone and its perforated texture."
In terms of noise, Car and Driver observes "the 2.4-liter GEMA engine...mostly hums quietly to itself and winds to high revs without major vibes." ConsumerGuide is less impressed, however: "the [Kia Optima's] 4-cylinder emits a thrashy groan at full throttle...the V6 is noticeably quieter but is less refined than most rivals V6s."