Reduction in mpg

[2 of the left]

My mpg has halved At one time I was getting 40 mpg now dropped to 24 mpg - Have had braking systems stripped and renewed - but cannot regain the 40 mark - Could this be slipping clutch - Wheel bearings are on top line - Ideas please!! Meanwhile Blue is in dock  -  New Coil overs,   Cooling System revamped and a/c topped

[Gaz mr-s]

Clean the maf & check the air filter.  If cleaning the maf doesn't work, try a new one. 

[Joesson]

@2of the left
There has been discussion on here about the negative effects of extra Ethanol being added to petrol, but your figures are way more than I recall being discussed.
A slipping clutch can reduce mpg but more immediate signs are usually noticeable.
In a convenient place, try putting the handbrake on and in first gear let the clutch out if the engine does not stall and the revs increase the clutch is on the way out.

[Alex Knight]

O2 sensors mandate fuelling.
Seems reasonable to start there.