[euromodder]

Originally Posted by Piwoslaw

I'm almost sure that you have same engine that I do

That's right.

Taking into account that we both have the same engine (and probably transmission)

MTX75 transmission in the Volvo.
That box is also used in other diesel and non-diesel Volvo's so it may not be the PSA gearbox.

I'm amazed that your fuel consumption is so high

Yeah.
OTOH, my overall fuel consumption is average on spritmonitor.de
The overall FC is only coming down since mid 2008 or thereabout, with the LRR tyres being fitted in Jannuary 2009.

When I drive it without paying attention to FE, I'll average 6L/100 km even when driving fast. Only city driving tends to push it even higher.
Fuel consumption can rather easily be brought down to around 5.5 L/100km by driving a bit slower.
However, getting it to 5L/100km is pretty hard, and going below that is a real challenge in this car.

Also, driving conditions in this congested part of Europe are far from ideal.

My car should average 5.6 l/100km, over 10% more than your's

The V50 is rated for 5.0 L/100km.
So it's easier for you to become a hypermiler

so I think it's the diesel particulate filter that's killing you.

It's in the exhaust path, and it does quite the opposite of all engine tuning tricks to reduce backpressure in the exhaust ...
So yes, it must have some negative effect on FE.

Is it the PSA's FAP filter, or does Volvo have its own

It uses the PSA technology with Eolys fluid - though I doubt the filters are the same externally.

Those filters are wicked!

I have had my share of problems with it, and it has taken Volvo until the 80.000km service to sort them out ...

Using constant throttle, the car would buck like a wild horse when the particle filter was burned free.
It'd accelerate and decelerate in rapid succession, which is then made even worse by involuntary movement of the throttle.
Sometimes it'd just slow down if I did nothing.

Pushing down the throttle always solved these problems instantly, but I wasn't happy with it.

Not only do they cause problem codes all the time, but they also require a high exhaust temperature to burn out every 500km or 1000km, so () the engine's computer will add more fuel when the burn process is in need to raise the exhaust temp. This causes your fc to go through the roof.

Though it's a lot less noticeable now, I can tell when the filter is burned free.
Fuel consumption can go up slightly, or even go down while the process is taking place !

I don't know if the Volvo onboard computer counts in the extra fuel needed to burn the filter free.

Since the last service - at 120.000 km - the onboard computer appears to be reading lower than it used to, and the difference between the indicated and actual fuel use is greater.

I don't know exactly by how much the dpf improves emissions, especially after 3-8 years of use

After 4 years, there were no measurable particles in the exhaust. 0 .
Normally, they usually read 2 to 4 (? units ?) even on cars with particle filters.

but I wonder if it is worth the extra fuel burned

I can't tell how much extra fuel it's costing, but on spritmonitor.de , there are a number of drivers with DPF and better FE.
However, my recent figures are becoming better than theirs

(The DPF was far more common in Germany than it was in Belgium at the time I bought the car - in fact the DPF added a couple of months to the delivery time ! )

or the loads of $$$ spent at the service station clearing codes, adding Eloys, or regenerating the filter.

Eolys is around 100 euro every 60000 km
The particle filter however, is almost 1000 euro's to replace (every 120000 km).
I didn't have it replaced at 120000km because it's not causing me any troubles anymore - don't fix it if it ain't broken - and to stretch out the total mileage the car will get with the new filter.
I tend to keep my cars for a long time.
If I can do so by replacing the filter just once instead of twice, that's a lot of easy money saved.

Many Peugeot and Citroen owners have dealt with the problem by removing their FAP and adding a sensor emulator to trick the computer

That's not the way I want to go.
The DPF is doing its job, even if it may cost a few mpg.

My car was tested in 2009, got a 2 year approval, so it's due for retesting in 2011, and yearly from then on.