THE 3 Series seats five people, though the longitudinal BMW engine layout makes designing a lengthy cabin more of a challenge than a compact V6. The current E46 version's longer wheelbase helps provide 20mm more knee room for rear seat passengers and 10mm more headroom than the previous E36 model, but the BMW's use of a straight six, which is also mounted further back than the C-class's V6, means it has slightly less rear legroom.