I have had my 159 1.9 jtdm 16v lusso auto for a month now - love the car - 57 reg but only 14000 miles ! apart from needing a new battery it seems fine. Since I suspect that it has had such little use in its first 4 yrs I did think that it would benefit from some diesel fuel addative - that and me doing 20k miles a year seems to have it running smoother and I have noticed a slight improvement in fuel economy. I keep reading on here about DPFs and Regens - What is a regen and how will I know that I am having one or need one ??
Basically some exceptionally bored euro mp's many moons ago decided that rather than diesel engines emitting their harmful exhaust hydrocarbons, all of the time they were running...they decided it would be far better for the environment if they were to trap all of these nasty little things, and then once every so often empty them in one big go. So we all ended up footing the bill with DPF's and EGR's.
The Diesel Particulate Filter, is the part that requires a Regeneration or regen, as it traps all the horrible nasty soot particles and that brown blackish smoke you see coming out of the back of some diesels when they accelerate.
So a regen is where the engine dumps raw fuel into the exhaust system (by firing the injectors on a non compression stroke) heating the exhaust gases to ludicrously high temperatures...
This burns all of the soot out of the filter, as you travel down a motorway or country road (somewhere where your generally doing more than 30 mph)
If the car didn't burn all the soot out, it would finally become so clogged that the backpressure in the exhaust would prevent the engine from running properly. So this is why the car will regenerate, when the pressure difference between both sides of the dpf is too high.
You will know when the car is regenerating by 3 telltale signs
1)There will be a distinct 'lack' of power, and boost will take longer to come in
2)The boost needle will drop like a stone to zero when you take your foot off the accelerator pedal, your current MPG on the trip computer will also be halved
3)The exhaust will have a nice throbbing boomy note to it.