BMW X5 E70 3.0d bad fuel consumption

[david2047]

Hey guys,

Does anyone one know why my car (07 BMW X5 E70 3.0d, 136,600km) has a really bad fuel consumption (15-16L/100km)?
Even I drive on a highway, it is still about 15L/100km.
I tried to reset the fuel consumption several times but I still got the same fuel consumption.
The engine light is on (yellow) when I power up the battery, but after I start the engine, it is off.

BMW dealer said they found faults with cylinder 3,4,6 glow plug and suggest replace all glow plugs and control unit, I'll replace all of them myself later.
I'm also gonna replace the fuel filter later.

I just wonder will the fuel consumption be about 11L/100km or better after the replacement?
I've already replaced the air filter and changing the engine oil (5W-40, full synthetic) and oil filter, it doesn't help to improve the fuel consumption.
Does anyone have a diesel X5? Could you share your fuel consumption with me?

Cheers