Citroen Synergie is a great MPV. I imported mine 12 years ago and it has done 200K miles. Uses very little oil as long as it is replaced every 6K or so.
I can do 700 miles on a tank and with 8 seats and a ample cruise speed of 75 MPH what more do you want? Sliding seats are a God send for kids. Great room at the back with seats taken out Why did they have to replace it with the C8?
Clutch lasted 113K miles

I have owned two Citroen Synergie 1.9TDs over the past 5 years, both were the 1.9 Turbo Diesel and both were 1998 model year.
The greatest compliment I can pay them is to wonder why Citroen ever stopped producing them.
2002 saw the demise of the Synergie when it was superseded by the C8. A far more thechnical car which produced far more tecnical breakdowns.
Back to the Synergie, the engines (if serviced regularily) seem to last forever, constantly returning over 40MPG, uses little oil and apart from a tendancy to use more heater plugs than normal, costs little or nothing in repairs.
The one draw back I have found with the 1.9TD is that it is a little sluggish on hills, this problem is common to this model and involves dropping down a gear or two to get up, what should really be a top gear hill.
That being said, it is the only fault with tis engine.
The interior is very functional, seats a little awkward to remove untill you get used to them, but once removed, you are left with a cavernous, van like space which I have had a 3 piece suite in.
The dash mounted gearshift takes a little getting used to but no problems when accustomed to it, in fact it leaves the floor space between the front seats clear to walk between to stop the kids from fighting in the back.
Handbrake is floor mounted between the drivers seat and drivers door so be prepared to reach to the wrong side till you are used to it.
17 Gallon fuel tank on these cars gives a mighty range when travelling long distance.
Stereo controls on the steering wheel, electric windows and sunroof with captains chairs on the "Exclusive " model.
Climate control works great and is very robust.
Driving position is slightly off centre of the wheel and pedals but soon get used to it.
Quite a wide vehicle, my missus has managed to smash the door mirrors on both of the ones I've had.
Rear sliding doors are a god send with the kids.
Problems to look out for

Excessive oil in the air intake.
Exhausts are expensive yet many other parts are not.
Heater plugs, a set of four = £14 but you will struggle to change the one behind the fuel pump.
Plastic sliding bush on the side rear doors wear quickly causing door to drop slightly.
If towbar fitted you have to keep repositioning the exhaust back box untill you get it into a position where it does not vibrate against the towbar when fully loaded.
Change the timming belt as per schedule (or earlier if possible) these are prone to belt snap.
Pads and discs easy and cheap to change.

The 1.9TD was superseded ny the 2.0 HDI, the HDI pulls slightly better up hills but MPG is similar and very little change on interior spec.

So in conclusion, these are remarkably reliable and large people carrier, now becoming very scarce in great condition, though rust is not a problem.
These engines, if serviced correctly are good for 250.000 miles and more.
Get everything but the kitchen sink in there and cheap to insure.

Happy to answer any questions on them if you have any.