Emissions software has increases the fuel consumption on my Audi A1 - what can I do?

I have an Audi A1 Sportback, bought new in 2012. Current miles on clock just under 33,500. Last month it went in for the emissions software installation and since then the fuel consumption has increased and having read similar report findings how can I prove that the blame lies firmly at Audi's door. My Audi dealer where I bought it from and had the software recently installed have agreed to look at testing it this week although I'm not convinced my pocket at the pumps will feel better for it as I believe Audi will probably take the line 'we rectified the defeat device and that's that'.

Asked on 28 March 2017 by Kathryn Causer

Answered by Honest John
VAG engineers carefully explained this to me on 1st March. Decreasing NOx emissions increases the amount of soot produced. To cope with this, the DPF needs to actively regenerate more often and uses diesel fuel to do this. For the engine to handle this without the car using more fuel, the remap alters the injection sequence, making the engine itself slightly more efficient - just enough to counter the extra fuel used by the DPF. To prove that the car is using more fuel, you would need to have kept a proper record of mpg, calculated on a brim to brim basis, that you can now compare to your mpg after the remap. Or, at the very least, you should calculate your fuel economy brim to brim now and compare that to the average for an Audi A1 1.6 TDI Sportback in www.honestjohn.co.uk/realmpg, which is between 51.2mpg and 57.4mpg (depending on engine and transmission). If your fuel consumption is substantially worse than 51.2mpg, then you have a case.
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