Wait – you mean automatic regens, rather than taking it to the garage?
You’ve got 40mpg and you’re doing lots of stop start journeys? That’s not too bad on a brand new car if you ask me.
Anyway – re DPF regen – there are two kinds, in VAG land at least (and probably others, BMW I think). There’s passive regen, where it advances timing and reduces EGR to get the exhaust temperature up. You should not notice this in terms of performance, but it might sound different. This uses no extra fuel, and will work fine in normal driving. If you aren’t driving it enough for this to work, it then initiaties active regen, which is where it’s squirting extra fuel into the exhaust stroke which oxidises on the DPF cat and increases temps to burn the soot. This would harm your MPG.
I think it tells you it’s doing this, because it doesn’t want you to stop the car when this is happening. If you do, it’ll then put a light on and according to the manual you need to take corrective action – take it for a dpf cleaning drive.
EDIT oh.. is your car not brand new? In that case.. on the previous thread.. some people are only getting 40mpg from their diesels.. and some are getting 60. There’s a knack to it, don’t expect the car to do all the work…