fuel suddenly guzzling and dropping loads

[ror888]

2004 old version focus hatchback 1.6 litre

for 100000 miles the mpg on my car was brilliant

I went on the motorway one night and got up to 77 but mostly at 70

and the fuel seemed to go down quite a lot and ever since then it has even for small journeys, which before would use hardly any fuel

why is the fuel all of a sudden going down faster?

is it air filter problem or tyre underinflation 

[artscot79]

what is it a Prius sorry but on o4 plate you're not getting 70mpg mate let alone 76mpg not even on a 1.6 diesel

[v530anh]

I get just over 300 miles on a full tank, no motorway miles on a 1.8 petrol. I would recheck the maths.

[south_bound]

2 hours ago, artscot79 said:

what is it a Prius sorry but on o4 plate you're not getting 70mpg mate let alone 76mpg not even on a 1.6 diesel

I think he meant he got it up to 70 mph (not mpg!) on the motorway.

 

There could be all sorts of reasons, but first thing I would do is measure the real mpg by noting the miles between fills and the number of litres used to get an accurate figure, otherwise you are just guessing.  It could be down to colder temperatures, shorter trips not warming up the engine enough, under inflated tyres (easy to check), time to do a service (cheapest place to start) etc.   You're not really giving us much to go on here.

[WES180]

2 hours ago, artscot79 said:

what is it a Prius sorry but on o4 plate you're not getting 70mpg mate let alone 76mpg not even on a 1.6 diesel

Ha ha. I initially read it as mpg too! Most economical Focus in the world if that was the case.

[mjt]

When the mpg on our old 2003 1.8TDCi suddenly took a dive it turned out to be a sticking brake caliper. Try feeling the wheel hubs after a decent run to see if one or more is getting unusually hot.

[goldtail77]

Any smell of petrol after a run?

You could have a leaky fuel line that only leeks when pulling\pushing through fuel.

As for Filter and Tyres, simple to check, so have you?

Let the car warm up at idle, then place a light coloured cloth over the exhaust. Is it dry and sooty or wet and stink of fuel? You could have a fuel\combustion problem.