Hey all,

Recently with the cold winter weathers here, I found that my consumption has gone really bad on my 530d - it's around 16L/100km on urban driving. Used to be around 10 or even less. I'm driving very gently, so no hard foot etc. On highway it's about 6.3L/100km, which looks OK. Temperatures are from -5C to -15C here currently. Dont think this winter temp. could cause that bad mpg drop though?
I got both thermostats replaced half year ago, so that aint a problem (coolant temp reaches 90C). My trips are very short on urban driving though: 2km and back mostly, everyday. Still dont think short trips could cause that low mpg.. as I said, it used to be around 10L or less, per 100km. Every weekend I mostly do a 260km trip to countryside aswell.

I'm suspecting the DPF myself. Half year ago I got diagnosed a faulty DPF backpressure sensor, but never really bothered to get it done so far yet. Could this be the cause? Read on some other threads recently, that when DPF starts to get clogged up, it will affect the consumption pretty much. Perhaps DPF has not regenerated at all, because DPF sensor has been faulty? I'm getting this DPF sensor fixxed now, and will let them to start the regeneration manually, to see if it helps. Or it might be already too late for that.. and I shall get the DPF "washed/cleaned" aswell?

Looking forward to hear your thoughts on this case!

Cheers.

 

Hi.

I think your diagnosing sounds good. It may be because of the DPF. Do what you're about to do and see if the forced regeneration will start and clean the DPF.

- Antti -

 

Ok will try to get it done asap and see how it goes. Just thought that clogged up DPF usually results in power loss tho?
By the way, is a regen possible at all, without the backpressure sensor?

 

A clogged DPF can result in power loss or then not. The symptoms vary a lot.
I don't know about the need of the backpressure sensor for the regeneration, sorry.

- Antti -

 

Those very short trips, especially stop&go urban traffic, are very detrimental to a big diesel with dpf. I'm not very knowledgeable on the Baltic climate but assume that it is often quite cold as well, meaning that it probably runs way below optimum temp. most of the time. Besides the filter problems this also increases wear and fuel consumption considerably.

If I were you I'd get a bicycle for those <10 minute trips and take the car on those country trips (will be good for the health of both of you )

 

Indeed. I agree it might run definetly lower than 90C coolant on those short trips.. but can it affect the mpg so dramatically? I had these short trips in summer aswell.. but MPG was OK then.

 

Yes it affects. When engine runs cold, it consumes lots more fuel.

- Antti -

 

Ok this might be one of the reasons aswell then.. I've noticed the temp reaches around 60C mostly, when I arrive the destination (urban driving)