Ford Fiesta mileage has fallen off a cliff

Jonathan_Powell

Hi all.

I drive a 2012, 1.25L Ford Fiesta. Not too long ago I could drive 250+ miles on a single tank. Now it seems I am not even getting half of that.

Today for example, the indicator said I had 8 miles left in the tank. After a short 3 miles round trip, it was saying 2 miles left. 

I have mentioned this during my service and nothing has come up (I do get it done through Ford so maybe they are just not looking properly). Is there a particular check that is worth doing? Or is this just the downside of having an almost 10 year old car.

oldagetraveller1

Rather than rely on "the indicator" I would carry out a brim to brim consumption check. i.e. fill up and note mileage, then at 1/2 a tank ot possibly less, fill up again and check mileage and volume of fuel added at the second fill up. A bit of arithmetic and you will have a good idea of m.p.g. for that distance. I prefer old school m.p.g. which means converting litres to Imperial gallons!

BOWFER

I'd get the MAF (mass airflow) checked.
If that is faulty or failed, the fuel to air mixture will be wrong and the car will be running rich all the time.
Common failures on any car.
Not an expensive or diffilut part to replace, easy DIY job.

Grumpy_chap

Jonathan_Powell said:

I could drive 250+ miles on a single tank. Now it seems I am not even getting half of that.

Today for example, the indicator said I had 8 miles left in the tank. After a short 3 miles round trip, it was saying 2 miles left. 

These are two different things.

Range on a tank should not drop from 250 miles to 125 miles.  Depending on the exact engine and driving profile, even 250 miles on a tank seems low for a Fiesta - my wife gets around 400ish.

As for the digital "miles remaining" - this is only really an estimate and in most cars I have had I find the remaining miles drop rapidly as you near empty.  Even to such an extent, I know I can do 25 miles in my Focus with "0 miles" remaining - not to be recommended TBH.  I think the car manufacturers build the "zero" point in with some buffer, so if you get stranded with no fuel, it is not their fault.  The fuel gauge and the "miles remaining" digital readout are useful guide but no more.

BOWFER

Grumpy_chap said:

Jonathan_Powell said:

I could drive 250+ miles on a single tank. Now it seems I am not even getting half of that.

Today for example, the indicator said I had 8 miles left in the tank. After a short 3 miles round trip, it was saying 2 miles left. 

I think the car manufacturers build the "zero" point in with some buffer, so if you get stranded with no fuel, it is not their fault.  The fuel gauge and the "miles remaining" digital readout are useful guide but no more.

Electric car GOMs (guessometers) verge on the cautious in a similar way, they all seem able to do surprising distances with the range saying zero.

Username03725

The range is based on current driving style & mpg, so it can extend again if you've done a few short trips then do a longer one. My Volvo will often show something like 160 miles left when we set off on a longer trip if it's been used for a few local journeys, then after 50 miles or so on the M1 at a steady pace the remaining miles has become 240, so that's 50 miles done and 80 more added on top. It is consistent though, the change according to its most recent use.

jimjames

BOWFER said:

Grumpy_chap said:

Jonathan_Powell said:

I could drive 250+ miles on a single tank. Now it seems I am not even getting half of that.

Today for example, the indicator said I had 8 miles left in the tank. After a short 3 miles round trip, it was saying 2 miles left. 

I think the car manufacturers build the "zero" point in with some buffer, so if you get stranded with no fuel, it is not their fault.  The fuel gauge and the "miles remaining" digital readout are useful guide but no more.

Electric car GOMs (guessometers) verge on the cautious in a similar way, they all seem able to do surprising distances with the range saying zero.

I thought that. I then tried it in my Audi and 0 range was remarkably accurate when I ran out of fuel!

elsien

If I was driving around with an indicator saying 8 miles left, the only trip I’d be doing is to the service station. Because in my car there’d be zero chance of getting 8 miles in it. 

BOWFER

jimjames said:

BOWFER said:

Grumpy_chap said:

Jonathan_Powell said:

I could drive 250+ miles on a single tank. Now it seems I am not even getting half of that.

Today for example, the indicator said I had 8 miles left in the tank. After a short 3 miles round trip, it was saying 2 miles left. 

I think the car manufacturers build the "zero" point in with some buffer, so if you get stranded with no fuel, it is not their fault.  The fuel gauge and the "miles remaining" digital readout are useful guide but no more.

Electric car GOMs (guessometers) verge on the cautious in a similar way, they all seem able to do surprising distances with the range saying zero.

I thought that. I then tried it in my Audi and 0 range was remarkably accurate when I ran out of fuel!

I've watched loads of CARWOW videos where they literally run EVs until they stop, I can't remember any stopping at zero.
I tend to only watch videos of EVs that apply to me, no point for cars I'll never own, so maybe missed the E-tron one.

Username03725

Jonathan_Powell said:

Today for example, the indicator said I had 8 miles left in the tank. After a short 3 miles round trip, it was saying 2 miles left. 

Just to pick up on this and building on what's already been said above, the readings for a 3 mile trek on a near empty tank won't be anything close to accurate, esp if you hadn't recently been out in the car. Assuming it's started from cold it'll barely be up to operating temp and a significantly higher proportion of the journey distance would have been accelerating in lower gears. The calculation will be based on the immediate consumption history which for a cold engine accelerating through the gears will be very low. Assuming there's about half a gallon in the tank, the calculated range will be much lower - 4 pints of fuel @ 20mpg will give a significantly different answer to 5 pints of fuel at 45mpg.

And these numbers that are displayed to the driver should never be anything more than a warning that fuel is low, and that you need to put some in at the earliest opportunity. A previous car of mine showed the remaining range down to 50 then just a dash - i.e. You're on your own now matey, all you know is it's less than 50. Anecdotally though the range does seem to give a pessimistic figure, allowing for a good few miles more on apparently fumes. Anyone remember Top Gear where Clarkson drove the Audi from London to Edinburgh & back? His range was close to 0 at Northampton and was at 0 by Milton Keynes. He made it back to the garage on the N Circular though, another 40+ miles on nothing acc to the computer.

Driving anywhere with 8 miles left let alone 3, in a Fiesta, is a particularly impressive stab at Fuel Gauge Bingo though. Well played.

ontheroad1970

Username03725 said:

Jonathan_Powell said:

Today for example, the indicator said I had 8 miles left in the tank. After a short 3 miles round trip, it was saying 2 miles left. 

Just to pick up on this and building on what's already been said above, the readings for a 3 mile trek on a near empty tank won't be anything close to accurate, esp if you hadn't recently been out in the car. Assuming it's started from cold it'll barely be up to operating temp and a significantly higher proportion of the journey distance would have been accelerating in lower gears. The calculation will be based on the immediate consumption history which for a cold engine accelerating through the gears will be very low. Assuming there's about half a gallon in the tank, the calculated range will be much lower - 4 pints of fuel @ 20mpg will give a significantly different answer to 5 pints of fuel at 45mpg.

And these numbers that are displayed to the driver should never be anything more than a warning that fuel is low, and that you need to put some in at the earliest opportunity. A previous car of mine showed the remaining range down to 50 then just a dash - i.e. You're on your own now matey, all you know is it's less than 50. Anecdotally though the range does seem to give a pessimistic figure, allowing for a good few miles more on apparently fumes. Anyone remember Top Gear where Clarkson drove the Audi from London to Edinburgh & back? His range was close to 0 at Northampton and was at 0 by Milton Keynes. He made it back to the garage on the N Circular though, another 40+ miles on nothing acc to the computer.

Driving anywhere with 8 miles left let alone 3, in a Fiesta, is a particularly impressive stab at Fuel Gauge Bingo though. Well played.

You're assuming they didn't cheat in any way on TG?  I admire your trusting nature.