The Mercedes-Benz E350 is a comfortable, quiet and luxurious sedan, with a well-finished interior, comfortable seats and a substantial feel. We tested gasoline- and diesel-powered versions. Both deliver punchy performance with capable handling. Two trim packages are offered, Luxury and Sport; we purchased one of each. Our gas-powered model was equipped with the Sport package, which provides a sport-tuned suspension, larger 18-inch wheels and a number of cosmetic changes. Our diesel-powered BlueTec model, which had the traditional Luxury package, provided a more comfortable ride and surprisingly, better steering feedback. The diesel model also returned considerably better fuel economy, but at a cost of some noticeable engine noise at low speeds. Some controls on both models are more complicated than need be.