I have a 2007 Astra Twintop diesel with 51,000 miles that I love, apart from a recent problem with the emissions warning light frequently lighting up. About eight weeks ago this happened on the way home from a long drive. The local dealer looked at it and said there was an air leak on the inlet manifold which needed changing. This was done under an extended warranty. About a week later the same fault recurred while driving back from Edinburgh to Cheshire, again halfway through a long journey at reasonable speeds. This time, however, the power died and I had to be recovered to a Carlisle dealer.

They identified a clogged EGR valve and a DPF that would not regenerate, and changed both. The EGR valve (the second replacement in three years) was covered under warranty, but the DPF is apparently a "consumable" filter and was not covered (almost £750). Since then I have had the emission light come on three times, in each case during a long motorway run. It's accompanied by a severe juddering for a few miles, which can be cured by running at high revs, which I understand is indicative of an incomplete DPF regeneration. However, when I return the car to the dealer he says there's no obvious fault but they have forced a DPF regeneration cycle which cures the problem for about 1000 miles. I'm a relatively high mileage driver with lots of motorway miles, hence the diesel choice. However I'm rapidly losing confidence with the car and the dealer. Is he missing something or am I?