My 520d has dropped to around 27 mpg from around 40, I have a company car know and the wife uses it for the school run, in 5 years of owning it we have done around 18 k,
It doesn't really get warm anymore so I'm assuming its a sensor or something like that,
Ideas please.

 

If it's struggling to warm up I'd put money on it being the egr thermostat, these often fail and when they do they remain in the open position, this means the other thermostat can't do its job as we'll so the car takes longer to warm up, as diesels use lots of fuel in their warmup cycle your mpg suffers

My 530d had this issue, was 23mpg round town, replaced the part for 20 quid, solved it, now it does a respectable 27mpg

 

I will have a look into that, what's it like to change?

 

Also on these, as mentioned in another thread, if there is a problem with the thermostats and the coolant temp doesn't reach 75 degs C the DPF won't carry out regeneration, and can soot up.

 

10 mins on a 530d if it's similar it's a piss easy job

 

Where on the engine is it located, any decent threads pointing it out?
Might do the swirl flaps aswell

 

Anyone have any info on this?

 

Have a look at the bmeer forums and YouTube for eng temp display workaround video.

Two stats and replace both together as your at it, only BMW part to as recommended ......

You can display eng temp on aux display to check stat operation as none on dash as you know

 

Dpf fault by the sounds of it