THE current Mercedes E-class has been with us since 1996 and still rates as the symbol of all that is desirable in the luxury class - even if it is under fire from the likes of BMW's 5 Series. The 3.2-litre V6 engine added in 1997 replaced the original in-line six of exactly the same capacity, adding more performance while reducing weight, fuel consumption and exhaust emissions. Otherwise, the E320 remains the masterfully engineered, spacious and supremely comfortable luxury sedan it has always been.