Mercedes-Benz has done all the right things to the C-class recently, with chassis tweaks and engine upgrades turning the junior exec into a very attractive proposition. But despite the carefully conceived changes there still remain some big weaknesses in the four-year-old C-class’s line-up, and one of the most obvious is the supercharged 1.8-litre engine used in the mid-range C230 Kompressor.A long time staple of the C-class range, the blown four-cylinder is endowed with considerable mid-range urge, but its coarse operation is very much at odds with the car’s otherwise cultivated character. No surprise, then, to finally see it being set aside for Mercedes-Benz’s excellent new 2.5-litre V6 petrol engine.The four-valve-per-cylinder powerplant forms part of a new range of engines that are set to be added to the C-class range and other models in coming months; the 3.0-litre and 3.5-litre units have already found their way into the E-class. It’s all part of a concerted effort to lessen Mercedes’ dependence on diesel engines. As good as they are, they’re expensive to produce and hold little attraction outside European markets.Confusingly, though, Mercedes has decided to retain the old C230 name with the introduction of its latest petrol engine – the practice of matching model designations to engine capacity is no longer the done thing in Stuttgart. Still, with prices set to remain the same in the UK, I suspect prospective customers won’t be too troubled by the retention of the old name, despite the engine’s larger size.Sit behind the wheel of the reworked C230 and you quickly appreciate just how much of a difference the new engine makes to the overall driving experience. Apart from the kudos of having a six-cylinder powerplant sitting up front, there is an immediate feeling of added refinement, no matter how hard you are working the car.The naturally-aspirated V6 is noticeably smoother and more free revving than the old supercharged four, with a more urgent feel from a standing start, and the engine quickly gets into its stride. It’s also a lot quieter than the four-cylinder, the improved sound deadening making long distance motorway journeys one of this car’s real strong points.The 2496cc engine features all aluminium construction, continuously variable camshaft adjustment for both the intake and exhaust valves and the the air intake has been modified for improved breathing. The result is 201bhp at 6200rpm – an increase of 11bhp. While the new model can’t quite match the impressive 192lb ft of its predecessor, its 181lb ft of torque is delivered 600rpm earlier than before at 2900rpm, and remains on tap through to a relatively high 5500rpm. The upshot is a more linear delivery, along with added flexibility when you put your foot down in the higher gears.The new engine adds an extra 40kg and, at 1530kg, the C230 is no rocket off the line; 0-62mph takes 8.4sec, 0.3sec longer than before owing, in part, to a longer final-drive ratio. But what this car lacks in outright acceleration, it more than makes up for with a wonderfully refined nature at high cruising speeds. It will happily sit at 120mph for extended periods without feeling at all strained, and the well-judged gearing helps to keep noise levels down.Less positive is the new car’s fuel consumption. Mercedes-Benz claims 30.3mpg on the combined cycle – down almost 2mpg on the old C230, itself hardly renowned for frugality. But whereas the old model required more expensive super unleaded to perform properly, the new one accepts cheaper premium, and it meets the latest Euro4 emissions regulations.So the new entry-level V6 helps bolster the C-class’s appeal. But this car isn’t just about the engine – it’s also about Mercedes’ 7G-Tronic seven-speed auto transmission. Available as an £1100 option, it replaces the old five-speed unit and plays a crucial role in elevating the C230’s refinement to levels that now make it a much tougher rival for the likes of the BMW 325i and Audi A4 2.0T FSI. We haven’t driven it with the standard six-speed manual ’box, though it’s hard to see how that could be any better than the smooth-shifting automatic.With superb damping, taut body control and a responsive rear-wheel- drive chassis, the C230’s dynamic qualities are also well up to the engine’s improved standards. Despite the added weight from the bigger engine, its ability on a B-road is highly impressive. The chassis’ inherent balance and poise should be enough to make the C230 attractive to even hard-nosed enthusiasts seeking an added touch of driving fun, and the added refinement endowed by the new V6 can only help.