Hi my 2014 econetic used to give around 57 mpg and would do 590 approx on full tank using figures from on board computer.  Now it only gives around 490 approx and 53 mpg and the only difference it seemed to start after I changed oil and filter which could be a coincidence also . Any one else seen anything like this or what are you getting from your focus thanks

Hello Barry. When did you notice the drop in economy? Economy worsens in winter. What you're experiencing is what would be expected during winter. 

I never got less than 600 miles to a tank on my Mk3 1.6 TDCI.  Average 55-60mpg.

490 miles sounds very low.  It's a 53 litre tank.  So even if you're filling up with 50 litres, at just 50mpg, you should still get 550 miles.

The low fuel warning comes on very early on these for some reason.  Mine would come on at around 90 miles range sometimes!  So it's worth checking the range as you may be filling up a little early.

Check the correct oil was used, if you don't know, change it again for the correct oil, ensure air filter is clean and dry and MAF sensor is clean also

The fuel filter being semi plugged can also cause decreased economy 

The correct oil was used and I checked air filter same time and last winter It never got this low.  Where is the maf sensor and fuel filter to check 

4 hours ago, cymro1973 said:

Where is the maf sensor and fuel filter to check

Fuel filter is on the engine, or near, MAF sensor is on the airbox lid

Hi OK checked Air filter and seems dry and fairly clean and cleaned maf sensor which brought the mpg up to 55 for few days and now its back to 53. Any other ideas ?

Have you checked fuel filter yet?

Revisiting this as my mpg has decreased to about 44mpg now on short journeys. Haven't checked the fuel filter yet, but would it reduce the mpg that much  ? Thanks

Anyone have any further help or ideas about this thanks

On 3/28/2025 at 9:03 PM, cymro1973 said:

Anyone have any further help or ideas about this thanks

Struggling to find reason for this anybody have any ideas or suggestions please

As said mileage varies a lot with season journeys, traffic etc etc...AND IMHO  brim to brim is the best (only) way to check due to vagaries of anything else like low fuel light etc. and even that's not perfect.

AND anything to do with fuel issues, just change the filter.

Ford say 3 years for ours but by then it's totally black and you don't know how fuel quality will change therefore I change every 2 years  - obviously depends on monitoring filter (cut it open) and depends on size and design (cartridge/can etc.)

Otherwise (assume diesel, I'm a one car Dinosaur guy) injector cleaner/EGR etc, something that is starting to fail at that age (2007, on borrowed time?)

Well, you sound desperate but it's not bad for a car that owes you nowt - sell it and buy a new better one with loads of problems to come!

51 minutes ago, Shearers said:

starting to fail at that age (2007, on borrowed time?)

You like me, read the profile of @cymro1973 which looks like it has never been updated.

I think the car in question is ......

On 1/25/2024 at 3:12 AM, cymro1973 said:

Hi my 2014 econetic used to give around 57 mpg and

It's confusing when the profile doesn't reflect the car being talked about.

12 hours ago, unofix said:

It's confusing when the profile doesn't reflect the car being talked about.

Confusing to the point of frustration (at least for me!) However 2014 is almost Jurassic depending on use/mileage so some of the comments still apply and will be interesting to see if there's a resolution?

Everyone after 2011 ALWAYS  gets 50+ MPG which I've seen once in my ownership (downhill with a following wind!).

56 minutes ago, Shearers said:

Everyone after 2011 ALWAYS  gets 50+ MPG which I've seen once in my ownership (downhill with a following wind!).

The S-Max isn't exactly lightweight or Aerodynamic tbf.

I've only ever had one diesel that couldn't manage 50mpg minimum.  That was a 2006 Vectra 1.9 CDTI.

All the others did - 99/00/01 306 2.0 HDI hatch & estate, 01/02 Golf 1.9 TDI, 08/12 Focus 1.6 TDCI, 04 A3 2.0 TDI, 12 Golf 2.0 TDI.

I've never had an MPV/SUV to compare though.

Best mpg was a 98 106 1.5 non-turbo diesel, 67mpg calculated over a tank...but I would gladly pay the extra fuel costs to never drive that again!    Easily the most dangerous car I ever owned.  Wouldn't go.  Wouldn't stop.  Wafted around in even the lightest breeze on the bridge.  Wasn't even easy to parallel park due to no PAS!

Sorry didn't know my old focus was on my profile I will change that. So its 2014 tdci 1.6

Surely if it  were fuel filter issue I would see some performance issues as well ? Had quick look down battery side do I need to remove something to get at fuel filter?

Nothing major needs to be removed.  I do still have this picture on the forum servers from bleeding mine back in 2018.  Shows the location of the filter.  You just need to remove a small bracket as far as I remember.

Changed oil and filter on this weekend after speaking to mechanic who thought it might be wrong oil in it. Still the same 45 mpg he didn't think it would be fuel filter as I'm having no performance issues but may as well change it to try?

Do I need to prime system after on mk3 tdci 1.6 ? I remember on older focus I had there was manual primer bulb on it 

Are you using cheapo supermarket diesel?

And I can't recommend this enough

https://www.ebay.co.uk/itm/371680538135

1 hour ago, cymro1973 said:

Changed oil and filter on this weekend after speaking to mechanic who thought it might be wrong oil in it. Still the same 45 mpg he didn't think it would be fuel filter as I'm having no performance issues but may as well change it to try?

Do I need to prime system after on mk3 tdci 1.6 ? I remember on older focus I had there was manual primer bulb on it 

Yes you need to manually prime the Mk3.  No electric tank pump and no manual bulb.

Yes I am using supermarket fuel but that shouldn't make a difference these days and I have never had fuel mpg issues like currently. I have already bought some wynn extreme diesel system cleaner so will put that in. 

Anyway back to filter as I haven't got pump to prime filter do we really think changing a filter will make difference ?

38 minutes ago, cymro1973 said:

do we really think changing a filter will make difference ?

In a word "No"

My thoughts would be a problem with the exhaust system being restricted.

Fuel filter can make a small difference, but it's pretty minimal. I have a C Max with the same engine, and my son has a Peugeot 2008, also with the same engine. The fuel filter on both of these is on the left hand top of the engine, under the top cover (as you stand in front of the car looking at the engine). It has a plastic lid, held on with four screws.

I've not changed the filter on mine yet, but my son's car has an in tank pump, and all you do to prime the filter is turn the ignition on, then off, three or four times before trying to start it.

Also, don't get too tangled up with the displayed mpg. At best, it's a computerised guess at what you are getting, and it shows an average, probably back to the last time the battery was disconnected, or the display was zeroed. The best way to work out mpg is to brim the tank, record the mileage (or zero the trip meter). Then use about three quarters of the tank, fill to the brim again, record the mileage and work out the mpg. For the record, my C Max display hovers just over 50 mpg, while my son's car shows he gets about 60 mpg (I do mostly short runs, with a good run about every two weeks, my son does a 32 mile each way commute, almost all on dual carriageways). So, the type of journey you are doing definitely affects the mpg!

Edited June 19, 2025Jun 19 by Alan G H
Spelling!

A few simple comments which are just opinions...
When was the fuel filter last changed? We had a limp mode problem when overtaking a truck uphill and never want that to happen again so clean fuel filter is top of my list, regardless of anything else.
I use Mityvac (or similar) to bleed, makes it very easy, reliable and none of that crank for 30s then wait, rinse and repeat, and hope it eventually primes before the battery goes flat and the starter is damaged!
Never found car MPG to be in any way accurate and never more than brim method (can be  5+ MPG or more difference)
Your mechanic "thought" that it may be wrong oil so you changed oil and filter with no effect. He  "doesn't think" it's the fuel filter so you aren't changing it (ever?) I agree that neither of those things will probably make any noticeable difference to MPG.
Weather, driving route, right foot etc are THE most likely things along with some other, yet unknown change if you have accurate long term records (our mileage pattern and range of values hasn't altered in 100 000 miles)
Hey Ho, just my view!