Engine problem with 2009 Yaris D4D ?

[adioldham]

I have a 2009 Yaris D4D. I have had to top it up with 5 litres of oil over 12 months, after just 20,000 miles.

Also, at random intervals, for no apparent reason, there is a big cloud of blue smoke, with an accompanying burning smell, from the exhaust. Again randomly, it starts to chug like an old bus as if it is about to stall but doesn't (cold or wamr engine, no difference)

The dealer doesn't think there is a problem with the oil consumption cos Toyota say that 1 litre per 1,000 miles is OK and at the 20K service said that "the new leaner greener engines use more oil" (!) but on the service report it then said "oil low, require oil consumption test after 500 miles". When I asked the service manager he said that the head technician was just being cautious" and that "the filters were a bit dirty is all " but the problems were still there next day
I feel that there is something badly needing attention

Can anyone suggest what could be wrong and what I can do next?
Thanks