Instantaneous MPG display and DPF Cleaning ?
 

I've had a couple of occasions while "steady state" driving where the instantaneous MPG nose dives. I was wondering if this was linked to cleaning the DPF and if others are also experiencing this.

For example - Motoway driving, 75mph, I-MPG ~ high 40s. then suddenly for a ~20 min period the displayed MPG drops to low 30's with no change in driving conditions. It recovers after some time. I have seen this a couple of times now - it may be happening quite often - I just happened to check the instantaneous MPG display.

Similarly today, driving around town, the displayed MPG was <10 - and there was a definite "burning" smell outside the car when I stopped.

sounds very plausible - never watched that readout, may do so now to see if I notice the same, would certainly explain the fuel consumption as I struggle to keep it above 34mpg (displayed, not calculated so it could actually be lower :( )

It will be the DPF. The engine has to produce enough power to heat the DPF to well over 700 degrees for it to work. On my current audi (multitronic) it felt as though the revs were too high and wasnt changing up gear for spells of 5-10 mins. This happened every 250 miles or so for the first 10000 miles or so but became less frequent as the mileage went up and began not to notice it.

It did take a bit of time to get used to and a trip back to the dealer when I though something was wrong only to be told its was normal.

Still, beats a big ploom of black smoke f the exhaust when you get over friendly with the right foot.

Thanks kj5cott.

It will be interesting to see if it happens less often once the car gets past 10K (currently on 8K).

Every 250 miles sounds very often, that's twice per tank of fuel.... When the sales guy mentioned I had in my mind that it would be every couple of thousand miles.

this might just explain why on some trips i seem to struggle to get more than 30mpg and then on a very similar journey i get in the region of 40. very frustrating

every 250 miles sounds a bit ridiculous, but hey what do i know!