We would recommend the powerful, super-smooth 3.0 litre V6 turbodiesel, which is closely related to the acclaimed engine in the Jaguar XF and XJ. There is also the four cylinder 2.2 HDi diesel which is more cost-effective, but people looking for cost-effective cars won't be looking at a C6 in the first place.
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http://www.verdictoncars.com/jsp/vocmai ... troen%20C6)
The C6 comes with either a 215bhp 3.0-litre petrol V6, a 208bhp 2.7-litre V6 diesel or a 2.2-litre, 173bhp diesel four. The big petrol motivates this big car from rest to 62mph in 9.4 seconds and on to 143mph, the smaller diesel takes 9.5 to 62 and gets to 135mph.
The V6 diesel is the best of the bunch though; 0-62mph in 8.9 seconds and a 143mph top speed make it on par with either of the other two and in-gear torque is miles better.
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http://www.topgear.com/uk/citroen/c6/verdict)
The choice 2.7-litre V6 diesel engine should also take credit. It's one of the most refined diesels available and is wonderfully soothing, though the hesitant auto gearbox means it's less rewarding when you increase your pace. There's also too much delay when pulling away, too. The 3.0-litre V6 petrol is cheaper, but much less impressive in practice
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http://www.autoexpress.co.uk/carreviews ... en_c6.html)