Normally on my commute of 37 mile motorway trip I average 44-50 mpg, this morning it's dropped down to 23mpg. I wasn't driving any differently to what I normally do, the car feels fine and the same as it always has done, the diesel gauge hasn't moved any more than it normally would have either so could it be that the mpg read out has just had a bit of an 'off day' today? lol surely if I was averaging 23mpg the gauge would be flying down?

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Boost leak?

Reset it for tomorrow and see how it goes (hold the reset button on the stalk until the mpg shows --)

Keep an eye on the temp gauge also to see if it does anything funny!

Would a boost leak cause an mpg drop like that? I've had a small one for a while but it's started getting louder recently. Didn't think that would do much thow to be fair.

Temp gauge has been fine always sat a MM below 90

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No a boost leak wouldn't cause that drop in mpg while car is still running fine

A boost leak is suggested by some forum nerds for any engine related problem it seems!!!

CTS failure on the boost channel but not on the guage channel?

Best go from full tank to full tank, recording mileage.

My opinion the on-board computer via the stalk is a joke, something to play with if you get bored..LOL

 

If performance unaffected, then stop worrying..

Little update, car is showing worse mpg everyday now it was down to 21mpg today.

Also, my weekly mileage to work and back is 371 miles yet my odometer only showed 280 this week?? :S really confused me, starting to think the clocks might have a fault with them or something ?

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Edited 13 February, 201511 yr by tommccabevRS

Ok, try this, which might help with diagnosis:-

 

Fill tank to pump pressure cutoff late Sunday or first thing Monday - Do week's commute and refill at same garage on way home Friday, if possible use same pump.

 

Calc fuel consumption as Measured Miles / ( litres bought (Fri) / 4,54 ) and look for the figure to be better than 45 for a healthy car.

 

We should then know if the issue is fuel burn (suggests sensor) or the trip computer.

Little update, car is showing worse mpg everyday now it was down to 21mpg today.

Also, my weekly mileage to work and back is 371 miles yet my odometer only showed 280 this week?? :S really confused me, starting to think the clocks might have a fault with them or something ?

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As suggested, one tankful to the next tankful with recorded mileage.

Suggest use trip meter against speedometer reading ?

You haven't said if you are making more regular visits to the fuel pump, are you making more visits?