2011 Vauxhall Zafira 1.7tdi
Fluctuating fuel consumption

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Singcobb
Driver
1 points

Problem added: Feb 23, 2020 (8 months ago)
Car starts and drives fine, but every so often the fuel consumption goes through the roof while I am driving. If I turn the engine off and start it again it goes back to normal. Sometimes it wont do it for days and then it will do it every few miles.

Car details
Car: Vauxhall Zafira
Variant: 1.7tdi
Model Year: 2011
Category: Engine & Drivetrain
Running Rough, Starting & Power Loss
Replies and Fixes
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whittingehame
Legend
15,353 points

Feb 23, 2020 (8 months ago)
If it is regenerating the DPF , fuel consumption increases .
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Singcobb
Driver
1 points

Feb 23, 2020 (8 months ago)
OK, first what is DPF. I am not talking about a small increase, if the car is ticking over it goes from .1 gallons per hour to .79, if driving it goes from 62mpg to 31mpg.
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whittingehame
Legend
15,353 points

Feb 23, 2020 (8 months ago)
A diesel particulate filter (DPF) is a filter that captures and stores exhaust soot (some refer to them as soot traps) in order to reduce emissions from diesel cars.

But because they only have a finite capacity, this trapped soot periodically has to be emptied or 'burned off' to regenerate the DPF.

This regeneration process cleanly burns off the excess soot deposited in the filter, reducing the harmful exhaust emission and helps to prevent the tell-tale black smoke you used to see from diesel vehicles, particularly when accelerating.

During active regeneration you will notice Increased fuel consumption which is perfectly normal
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Singcobb
Driver
1 points

Feb 23, 2020 (8 months ago)
OK, but should this happen so ofter? This is every time I drive the car.
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whittingehame
Legend
15,353 points

Feb 23, 2020 (8 months ago)
If the car is used for short journeys this is common .
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Singcobb
Driver
1 points

Feb 23, 2020 (8 months ago)
thanks
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whittingehame
Legend
15,353 points

Feb 23, 2020 (8 months ago)
Why does the DPF need regeneration / cleaning ?
The DPF filter traps carbon particles, filtering exhaust gases as they pass through. Like any filter this must be regenerated (cleaned) to restore it to full operation. Under normal circumstances the regeneration process is carried out by the car itself when the engine/emissions management system detects the DPF is in need of regeneration. However Diesel vehicles used only for short journeys do not provide the system sufficient opportunity to regenerate the DPF, resulting in a fault developing.

Failure to have the regeneration completed at this stage could render the filter itself beyond repair and require complete replacement. A DPF that reaches 90% or approx. 45 grams full will be beyond regeneration and require complete replacement.

Depending on your vehicle make and model a failed Diesel Particulate Filter can cost upwards of £1000 to replace.
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