MPG much lower after a service

[d_taddei2]

I had my Seat Leon 1.6tdi 2014 serviced a week ago and from the first day after the service until now the MPG is terrible around 20 mpg less can't even get it over 60mpg prior to the service the worst I got was 63mpg but I was consistently getting 68-75mph and on occasion 80-86mpg. Not sure why this has happened any ideas? Wrong oil type? Wrong fuel filter?

 

[SuperV8]

Are you comparing the same MPG reading as before? There are three different average MPG's to view and also an instantaneous MPG. Has the cluster just been changed?

 

[d_taddei2]

Hi I have checked both spontaneous and average, but I normally go by the average. Similar journeys and same types distance and road surfaces, I did the exactly the same journey the difference was 25mpg less which I think is pretty obvious something not right. If it had been 1-5mpg difference I wouldn't really notice but 25mpg is a big difference the hasn't been over 60mpg and struggles to get even 55mpg mostly 45-50mph now when before my worst was 63-65mpg

 

[SuperV8]

There are three averages! - which one did you used to use, and which one is it on now?
1. long term?
2. since refuel?
3. current journey?
Try toggling between them?

Everyone knows (should know) TDI's use 507 spec oil which is 5w30 or 0w30 - There is no way using the wrong oil would loose you 25mpg!
Was this a main dealer - or an independent?

 

[d_taddei2]

Hi I always use current journey, I have done over 200 miles since service, the car was reset during service and again a week later when I had the recall on the airbag done, the issue is the same. It's an Independent garage and car has been serviced there before. I still have to check the air filter as I read online that if it's not fitted correctly or wrong one it gets the mix wrong and uses more fuel apparently. The car drives normally.

 

[SuperV8]

I don't see how a garage could incorrectly fit a flat panel filter? unless they left a rag in there!
What did they do? Just an oil/filter change?
Have you got an OBD2 bluetooth reader? I think I would scan for fault codes to see if anything comes up for your DPF/alternator/AC compressor?
Could you have had a bad batch of fuel? If that's even possible?
When was the last time it had a fuel filter? though if the fuel filter is blocked you should get a warning and limp mode.

 

[d_taddei2]

I heard of it not clipped in properly (air filter) it can cause mix issues. I don't think it's fuel. Fuel filter normally gets replaced as part of the service along with plugs, oil filter, air filter. I will give it another week before I go back to garage and ask.