Can a "bad tank" do this?

[darve]

2014 Audi A5 Diesel

Since filling up there is a noticeable drop in MPG. Drive to work normally averages 60 MPG on the car computer (I know not true MPG but gives a benchmark). Same journey since the fill up and struggle to get 50 MPG.

Can notice the auto box hangs onto a lower gear which naturally won't help. Manual shifting up doesn't help as the "live" MPG drops so the higher gear must labour the engine more

Can a bad tank of fuel cause this ?

Tyre pressures look ok (not checked with a guage) and it was serviced a few months ago

P.s. not very exciting I know....

[Kit Car Electronics]

No, but you could be coincidentally going through dpf regen would be my guess

[DE04*]

No, but you could be coincidentally going through dpf regen would be my guess

dpf regen

[darve]

I'll go Google DPF regen

[Kevin (Mr T)]

Does Mike make this stuff up?

I was thinking it could be an apg bertie issue!

[darve]

Should I do anything Mike or just let it do it's thing? Drive hard / higher revs?

[stephenh]

Did you get the same fuel as before, and from the same source?

[darve]

Same place. Just standard deisel

[XTR2Turbo]

Diesels can also be very sensitive to cold temps. Especially if fitted with auxiliary diesel powered water heater. On my disco this cuts in when ambient below 12,c

[DonPeffers]

As you mentioned in OP best check tyre pressures with accurate gauge as much colder air will have caused pressure reduction and I don't rely on the dash light to tell me.

[DE04*]

just googled dpf regen,every week i give my taxi a very hard rev nearly to max and the smoke that comes out the exhaust you can't see through (always do it at night or when I pass cyclists that are taking up all the road)  but seems to drive better afterwards

[DamperMan]

Maybe the compulsive VW lies have stopped, maybe it thinks your not looking! 3.0 V6 ? Getting 60mpg I'd suggest going a bit faster as the milk delivery behind you will be getting late ... My tiddly 1.9 PD struggles to top 45mpg on brimming the tank each time. I'm always impressed when the light comes on, I can get 56l in a 55l tank!... I digress! .

Drop in MPG could be one of millions of things. I bet it's the gyro cog loose !

[tim]

Change the diesel filter for a start,more than likely full of muck !

[darve]

Looks like Mike was correct.... again....

Gave it a hard blast for 20 miles or so and back to normal now

[Ben30R]

Can always tell when mine is due a good blast (re gen) fan stays on for quite a while after driving. 20min over 2k job sorted