Hi, im not sure if anyone can help but I thought id give you a shot

I have had a 1.6 Fiesta for just over 6 months and usually when I fill up (I always fill a full tank) I get a range of about 600km's according to the trip computer. The past couple of weeks when I've been filling up I've only been getting a range of between 570-580km's though.

I've also noticed when I drive my trip computer drops the distance quite substantually and might suddenly increase as well. For example today when I went to work i had a range of 350km and when I arrived I had a range of 302kms. The 48km drop seems a little excessive for my 10km drive. it wouldn't surprise me if i get in to go home and see a range of 330

Ive checked my tire pressure, haven't added any extra weight to the car and my led foot hasn't gotten any worse over the past couple weeks so im not sure what the issue can be

Ford said it might be a faulty fuel transmitter, but at $800/ 670 pounds for them to check and it might not even be the problem im not keen on that exercise.

Does anyone have any suggestions of what can be causing my sporadic trip computer/ fuel consumption?

If the way you drive hasn't changed and the ambient temperature and pressure are similar, then it can only come down to a mechanical fault. The spark plugs might be the cheapest suspect to swap out and the air filter might be blocked. Check the brakes aren't binding, the fuel is the same. The engine sounds as sweet as normal?

Before you replace anything, try to do a few tank fillings more, completely full, but now write down the amount of kilometres you've done and then divide that number by the litres you refuel. That's much more accurate to see if there is a problem. Only the distance without the amount of fuel put in doesn't say anything.

And if you only drive 10 kilometres, you won't get a very good fuel consumption, engine will be hardly warm, let alone be on working temperature. So if the outside temperatures will be a little lower then before you're fuel consumption will rise quite a bit, it will inject more fuel as long as the engine is cold/luke warm. (Used to work 15 kilometres away, the difference in fuel consumption between summer and winter was a lot (summer 16 km on a litre, in winter 11,5-12 km a litre), engine hardly got warm, in general it takes about 10 km to warm up the coolant but 20 km to warm up the oil. Now i have to drive 70 km to work and the difference is much smaller because the time driven with a cold engine is only a small portion of the way instead of about all the way. (17 km a litre in summer and 15,5 km a litre in winter.) )

That won't make much of a difference when driving long distances but on such short trips it will increase the fuel consumption dramatically.

So as it's going to be fall and winter, expect the distance to be driven on a tank of fuel to decrease substantially.

On the bright side, it will increase again next spring/summer ;)

I gave my dealership a call and turns out that my last service was a major one with all spark plugs, filters and oil being changed. They suggested that I try putting a higher grade of fuel in for the next couple of tanks to try and cleanse the engine. So I thought I would give that a go.

Actually when you mention engine sounds, sometimes when I start up in the morning i can hear a sort of rubber squeak coming form the engine. Once the engine is up and running though it disappears though

Thats a good idea Gombal - I guess Ill start writing down mileage when I fill up to see if it is actual fuel economy playing up or if it is just my trip computer.

Well once a week I do an 80km drive each way to go to University and this week it used more than usual. I forgot the exact figures but I was surprised at how low it was. Also living in Australia our seasons are reversed to your English ones, so I am getting hotter at the moment not colder, so hopefully I can enjoy better fuel mileage ;)

Oops, didn't see you were from the other side of the globe :) .

I'm not from England but from Holland but that doesn't make any difference with the seasons, weather is getting colder already so my mileage is going down.

Curious to see if it's just you're trip computer or really a problem, i think the first but time will tell.

So I've given it two weeks now and have refuelled fully after a weeks worth of driving. I always like to have a full tank at the beginning of the week so I can do as much driving as I want ;)

week 1, (130770 - 130514)/22 = 11.64

week 2, (131096 - 130770)/26.9 = 12.12 (this tank was 95RON instead of 91RON)

Considering my recommended combined fuel consumption from Ford is 6.6L/100km I think something might be up. I know I'm a lead foot, and do a bit of start stop city driving but having fuel figures that high from a 1.6L 4cyl is not ideal. The V6 in the house uses about 12L/100km

The engine generally runs smoothly, with no power problems and sounds fine. There is a rubber squeak some cold mornings but that generally goes away once the engine has warmed up. I asked my Ford dealer who services the car what was done at the 125,000km service and they said all the spark plugs and filters were changed.

Anyone have an idea as to what is up with my excessive fuel consumption?

Still think it's the short distances, our Suzuki, only a 1300 cc, has about the same fuel consumption as your 1600 cc even though we reguraly drive 40 km with it.

When the engine hasn't reached it's working temperature it will inject more fuel and in general it takes an engine about 10 km to warm up (coolant) and about 20 km to warm up the oil. The fact that the coolant temp has risen to it's normal point doesn't mean the oil is at working temp, takes about twice as long.

So every time you drive you're running in the most unfavorable way as to fuel consumption.

About you're lead foot, the thing that has the most impact on fuel consumption is when you go off the gas at the last point before braking. When lifting and releasing the throttle a good way before an intersection or traffic lights will save a lot of fuel because when coasting down in gear there is zero fuel going to the engine. This can bring up you're fuel consumption up as much as 2 km/ltr (or even more if perfected).

If you really want to know you should drive about 100 or 200 km in one go, preferably one long stretch highway or motorway (don't know what it's called over there ;) ) or country roads with out to much stopping and pulling up at a steady speed (80/100 or 120 km/hr). (And if you happen to have cruise control it would be even better)

Fuel up to the brim before, reset the fuel consumption thingy if possible and make the run. Fill up to the brim afterwards and i think you will be amazed at the difference in fuel consumption compared to the figures you just posted.

(FYI, Our Suzuki managed 17 km per litre max one time (only 60 and 80 km roads whilst on holiday, all flat, no hills over here) Whilst driving to work (used to live 15 km from work) it averaged 13,5 to 13,9 km per litre. Now because my wife only drives very short distances (1 km to 10 km) it averages about 12,5 km per litre. In winter even less, 11,5 km/ltr. All these figures are no where near the manufacturers fuel consumption figures. My colleague has a 3,2 litre V6 Mercedes which is almost double the weight of the Suzuki and 2,5 times the engine size (same age, Suzuki and Mercedes are from 2000) and he averages 10 km per litre so little engine doesn't alsways mean low fuel consumption.)

O, also tires have a great influence on the figures, used to have Michelin Energy's on the Suzuki, switched to Vredestein (dutch ;) and cheaper) and the kilometres per litre dropped 1 to 1,5 km/ltr just because the Michelin were a lot more economical (different compound etc) So in the end i would have earned the price difference between the Michelins and Vredesteins in 6 months and after that i would save more on fuel by having the Michelins. But that's a lesson for the next time i buy tires.

Also driving with a little bit more air in the tires can help a lot (personally drive with 2,5 to 3 bar in my tires), driving with the tires to soft will also increase fuel consumption (and more tire wear and more prone to puntures)

I also have an old Mercedes W124(250D, 1986), when driving to work now, about 85% highway at 120 km/hr, 15% countryroads (80 km/hr) and city traffic, it easily gets 17 km/ltr. When driving to my colleague all week (we carpool), only 12 km away (50% 100 km/hr and 50% 80 km/hr) i can't get more then 12,5 - 13,0 km/ltr! (Same weather conditions etc.)

To make a long story short, i still don't think you're fuel consumption is strange, lead foot and short distances will kill any good fuel consumption, no matter how efficient and economical your car is.

I first wanted to say take a look at the airfilter but all filters were changed so a (partially) blocked airfilter can't be the case.

(A long, faster run will also benefit your cat, everytime i take my wifes car, the Suzuki, to work (130 round trip with the 85% 120 km/hr) she says it's almost a different car, much more responsive. On the long runs the cat can burn clean and also the inside of the cilinders/valves etc will burn clean. I try to do this once or twice a month, also benefits the battery in winter, then it will get a good full charge.)