It's the 1.6 HDi Peugeot engine. I have a 2010 1.6 DrivE S40 R Design. It is an utterly superb car, when it's 3 years old I'll order another straight away, currently with 42k on the clock but still drives just like a new car. There's not a creak or rattle or any signs of wear. It did 36k on it's first set of front tyres and is still on it's original front pads. It does 45mpg at 99mph and around 60mpg at 70mph (not very often).
I cannot praise this car highly enough.
They do have a particulate filter which is the diesel version of a catalytic converter. Because Diesel is slow burning this filter can clog so it has an internal facility where an octane liquid is injected into the 'cat' super heating it and therefore de-coaking the 'cat. This all happens automatically while you drive, probably once a month or so. The consequence of this is that eventually the octane liquid runs out at the lifetime of the filter and both have to be replaced which is pricey. This is usually at about 50k miles.
I used to work in a Peugeot main dealer and often our technicians would be up in a corner of the compound doing a manual clean using a diagnostic laptop.
It's a strange sight watching a technician standing with a laptop on the roof while the car goes through various rev cycles!
HTH
