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MPG much lower after a service
- Thread starter d_taddei2
- Start date
To be fair I hadnt heard of that so looking on a load of forums it appears on a lot of cars there is not only the oil service required light but also a sensor linked to the DPF which also needs resetting so the car knows there is fresh oil - otherwise the car wont regen.
In your car are you noticing the revs higher at idle, burning smell or the stopstart not working? These are the classic signs of the dpf regenning.
How many miles did you get out the most recent tank?
What is performance like as well - is it like normal or had that gone down as well?
In your car are you noticing the revs higher at idle, burning smell or the stopstart not working? These are the classic signs of the dpf regenning.
How many miles did you get out the most recent tank?
What is performance like as well - is it like normal or had that gone down as well?
If you’ve not got a suitable diagnostic scanner, I’d ask the garage if they would check the soot levels and the amount of ash build up in your car’s DPF first rather than just reset it. If it is blocked then that would probably explain your mpg deterioration as the regen frequency would be high in trying to clear the blockage. A DPF with a severe blockage would require cleaning or possibly replacement.
Ok thanks for the advice. I normally drive around 650-700 miles a month with quite a lot of it longer journeys and do a diesel redex clean every year. The car has effectively been reset twice once with for the service with independent garage (mpg worse), then again after the recall at seat garage where mpg got even worse
Ok so true mog is around 60mpg, how many miles did you get out of the poor mpg tank?
Has it just been one tank as I am wondering if the car is suffering still from fuel contamination, my friends TDI is only just starting to get back to normal after several decent tank fill ups.
Has it just been one tank as I am wondering if the car is suffering still from fuel contamination, my friends TDI is only just starting to get back to normal after several decent tank fill ups.
I normally get a reading of 65-75mpg worst was 63mpg. I never let the tank get low so probably could have done far more miles. I was still using fuel from the tank when I was getting a reading of 65+ in fact a week or so before that I got 86.4 driving mostly B roads with a few A roads over 40+ miles journey, then while still using the same fuel I Then suddenly after a service I couldn't get it above 55mpg on any journey. Then since the recall I am getting 35-47mpg. I have in the last few days put a full tank of fuel back in. It's very odd can't think of what could have done it. I also read somewhere the VAG do an update on the car and it purposely brings mpg down so car is less fuel efficient and my car likely got an update at the recall. But I can't 100% if this true.
That update you are talking about is potentially the one following the emissions scandal where some owners reported after the update their mpg went down.
What i would do is the brim to brim method and work out for definite what the true mpg is as the trip computer could be way out.
The revs look higher than they should be, usually because it is completing an active regeneration but you dont have the smell to go with it so I wonder if it is stuck.
What i would do is the brim to brim method and work out for definite what the true mpg is as the trip computer could be way out.
The revs look higher than they should be, usually because it is completing an active regeneration but you dont have the smell to go with it so I wonder if it is stuck.
If you got 700 miles out of a tank which is 50 litres that's works out at 63mpg not the 83 you have quoted!
Even only using 40 litres is 79 mpg
Even only using 40 litres is 79 mpg
Please read my post I stated that on one journey..I never stated I got 83 through the whole tank that would not make sense. Mpg varys on journey my average on a poor mpg is 63. My best was 85.3. these are my average per since start for each journey when I checked the car before reset my since refuel was averaging 65-68 most of the time. And long term it was 66-67 I would never drive the car dry of fuel so saying 700 on 50l isn't practical that would suggest that I drone the car until it ran out of fuel which isn't the case I would get around 700 to the point I would then fill up normally with 1-2 bars left on the fuel tank. Hope this makes sense
Interesting I just filled up a few days ago. A blunt two weeks after the service and a week after the recall. I might call the seat garage and see what they say. But even the independent garage stated that my mpg should be higher than it is. A friend has a 1.9tdi and he's getting around 55-65mpg I ain't even getting that. I personally have noticed fuel consumption has been higher than normal.
Yeah that sounds very low mpg indeed, are you getting any black smoke out the back when you accelerate hard?
As I mentioned a while back - check your DPF - 1000rpm idle is a sign its doing/trying to do a regen.
The Independent garage mention a smoke test for vacuum leaks. Need to try and eliminate potential causes. Thanks the suggestion
I know this might sound silly, but they haven't adjusted the tyre pressures during the service have they?
I.E you usually run them at say 42PSI for maximum MPG but they've set them to 36PSI?
I.E you usually run them at say 42PSI for maximum MPG but they've set them to 36PSI?
^^^^ Another shout out for 'winter diesel' now being in your tank plus tyre pressures. 
Guy
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Guy
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