Turbo/intercooler maintenance?

[marshallarts Junior Member Find all posts View Profile Close marshallarts]

My 2008 diesel manual is approaching 450,000km. I'm a bit obsessive about fuel consumption (hate burning diesel!), and have a ScanGauge to keep track of what is going on, from minute to minute. I have noted recently that headwinds when towing our very small caravan (12ft, loaded weight about 1200kg) seemed to be having more effect on fuel consumption than I remember from previous years. But then just yesterday we did another leg of a biggish trip, again into a howling headwind, and the fuel consumption was surprisingly reasonable. I was quite taken aback. It was at least 2 litres per 100km less than I would have expected in the conditions. The only factor I can think of that might have made the difference this was that it was much cooler weather than most of the rest of the trip - only 15-16 degrees outside, instead of well into the 30s. So this got me thinking why cooler air could have such a dramatic effect on fuel consumption. Anyone got any ideas? Does this tally with anyone else's experience? I was wondering if maybe the turbo and/or intercooler maybe need some maintenance - decarbonising, cleaning, or something? I am not very mechanically knowledgeable, but I can certainly accept that after 450,000km something might need doing. I had often noticed on previous trips that if we continued driving into the evening, the ScanGauge would nearly always show a slight but definite decrease in fuel burn as it got cooler outside. But I've never seen a difference as significant as this. Any thoughts welcome.