I'm not just relying on mpg on car computer I know from records when filling up I'm getting lot less. I'm not saying I won't cha ge filter but is this the cause of my issue now probably not?

Update last night engine service warning came on diagnostic says P2598 turbocharger boost control position sensor A performance - stuck low 

Check the thin rubber pipe from the vac pump (just in front of fuel filter) to the boost actuator.

If you're not getting enough boost then that will affect fuel consumption.

If there's now a code, that was my point about another as yet unknown fault - which may now be known?

Hope the vacuum pipe or other solution is found!

Hi do you mean this pipe I'm pointing at below not sure where the boost actuator is ? 

1 hour ago, cymro1973 said:

Hi do you mean this pipe I'm pointing at below not sure where the boost actuator is ? 

Yes.  But that's where I was expecting it to be broken anyway.

If you can follow that white pipe back as far as possible, and the black one next to it, both of those are vacuum pipes.

The turbo actuator is on the turbo itself, but there will be a solenoid somewhere in the pipework that controls the vacuum to it.

With the current fuel situation am re visiting this problem as nothing has improved since last post. I did check the white boost pipe above and cleaned out a the time. On a long journey I am getting about 57 but on short local journeys it goes down to about 44 so giving me only about 450 miles on full tank. Any further ideas to check ? Thanks

Actually those MPG figures sound amazing! (but we have the large frontal area shed that is S-MAX)
If the code (or any code) is still present then that still needs tackling.
Whilst you've checked the pipework, the actual solenoid controlling the vacuum applied to the turbo actuator is mentioned above but you don't say if that has been tested or changed?
This post gives an idea of possible faults with one specific type of actuator:
https://www.fordownersclub.com/forums/topic/166556-turbo-boost-fault-limp-mode-solved/

On 4/10/2026 at 2:27 PM, cymro1973 said:

With the current fuel situation am re visiting this problem as nothing has improved since last post. I did check the white boost pipe above and cleaned out a the time. On a long journey I am getting about 57 but on short local journeys it goes down to about 44 so giving me only about 450 miles on full tank. Any further ideas to check ? Thanks

You said last year that you use supermarket fuel.

I am guessing here, but if you are using fuel from Asda, or even EuroGarages (same owners), around here they have a reputation for not giving good MPG, to the extent that my son and several of his work collegues have stopped using their diesel. I would suggest you try using fuel from one of the bigger brands for a tankful or two, and see if it improves.

At the present time, there is not much difference in price between filling station prices, they're all expensive!

As to the difference between different suppliers of diesel, the basic fuel nearly all comes out of the same tanks at the distribution depots, but each brand uses different additive packages, which can effect the fuel consumption figures.