Thanks Tombie2, that's always a good idea.
Every now and then I also put a bit of diesel detergent. It's supposed to be good for the injectors, but I assume that will help in keeping the all fuel system clean.
The engine runs very efficiently, the average fuel consumption over the entire year of 2009 is 9.2 Ltrs per 100 Km. I keep an absolute account of fuel and millage.

