Hi all,

I have a 2000 1.4 8v mpi fabia, 56k on the clock. On my 120 mile daily round trip (all dual-carriageway) i would normally return 40-45mpg depending on whether i drive like a priest or drive like my trousers were on fire. But about 3000 miles ago i noticed a large downturn in my mpg, since then i have been returning 36 mpg at best. But with no visible signs of a problem or engine management lights i continued until my xmas break. But this weekend i performed a full service, the car is reguarly serviced every 5000 miles by my brother who is a Kia Mechanic, It is also fastidiously maintained.

So to try and determine a problem this weekend i changed front discs and pads, and rear drum shoes (needed doing anyway) figured that there maybe a binding problem. Air Filter, Oil filter and oil change, changed all the plugs (no signs of any inefficient burning). I havent changed the fuel filter as yet because i was supplied with the filter for the 16v model. So unless it is the fuel filter i cant see it being an engine problem, there are no gasket or oil leaks, no exhaust problems. Anyway after doing this, after a round trip today i returned 36 and 38 on the way home, this wasnt driving with excessive revs and a cruise of around 75-80mph, 3500 rpm, average speed of 60 mph according to trip comp.

There is another issue which maybe causing the problem, round about the time that i had noticed the change in mpg i had all four tyres changed. Now i would maybe expect a 1 or 2 mpg deviation due to different tyres being fitted, but not such a great amount of change. The tyres i had fitted arent ditch finders, they are mid range tyres, 4 Falken tyres (£180), granted not Michelin or Pirelli. When first fitted they werent balanced properly so i took them back and that was rectified. So it seems logical with the tyres are the issue but i just cant see them having such an effect myself.

So im just hoping that i will replace the fuel filter and all will be dandy but i doubt it. Im asking you gents if you have had or heard of similar problems or if there are problems intrinsic to my particular model that could be causing my problem. I have thought of taking it to my local dealer but dont want to pay through the nose to be told they dont know whats wrong as me, and my brother and father, both experienced mechanics cant see antything wrong. All we can do is lean to the fact that it must be the tyres, in which case i will stump up for some Michelins, as travelling 600 miles a week and doing 60-70 miles less on a tank of fuel im paying through the nose.

Well i apologise for going on but i just wanted to get everything across, so any help at all would be greatly appreciated.

Regards

Tom

quick question??

what does the car drive like when it's stone cold?? and what does the temp guage do??

it could be a faulty coolant sensor causing the ecu to pump more fuel in

Well i drive it stone cold every morning (setting off at 5.30am) it seems fine, well its how its always been, not noticed any difference since i bought it 16k ago. It can be a little stuttery but thats due to me applying a lack of revs when moving off but anyway. The temp gauge has always risen steadily too bang on medium and never gone above, even in the hot summer we had, just figured this was due to good cooling.

120 mile trip to work. 240 mile round trip. 5 day week 1200 miles.

3000 miles = 2 1/2 weeks.

Start of the colder weather and, mostly, winter diesel possibly partially responsible (less calorific value than normal diesel).

Also if you're running the heater more to keep warm, and also the car will take a little longer to warm up in colder weather.

Plus, as you say the new tyres may be less energy efficient.

Back to the winter diesel - a few weeks ago a whole slew of owners were asking why their fuel consumption had suddenly increased.

Sorry - missed the bit about 600 miles a week.

So, 5 weeks ago your problems began. Winter diesel may still be main culprit - don't know when they start supplying filling stations with it though.

On a run mine gets around 40-43MPG , I get 36MPG around town! (Both trip computer figures)

120 mile trip to work. 240 mile round trip. 5 day week 1200 miles.

3000 miles = 2 1/2 weeks.

Start of the colder weather and, mostly, winter diesel possibly partially responsible (less calorific value than normal diesel).

Also if you're running the heater more to keep warm, and also the car will take a little longer to warm up in colder weather.

Plus, as you say the new tyres may be less energy efficient.

Back to the winter diesel - a few weeks ago a whole slew of owners were asking why their fuel consumption had suddenly increased.

I do 120 miles a day, not 240 god forbid, and its a petrol car lol, and Dmac i dont drive in cities, i live in selby south of york and work in Northallerton, so straight up the a1 and a19, so either 2 or 3 lanes, so not city speeds or mpg in consideration.

Oops - jumped the gun.

Ignore most of what I've said, obviously.

Didn't get much sleep last night - my excuse anyway.

haha no excuses, thanks for having a shot anyway, appreciated

Just can't believe I dropped so many ******** - unlike me.

Mind, I am downloading, searching, checking emails etc - but then again I usually do this AND get things right (I'd thought it was the 1.4 TDi).

Anyway, you're spot on for checking things over. I always brim to brim and note the mileage - then if it drops I know something is amiss.

Just one leetle suggestion as a last resort before you go 'the expensive route' - the fuel filter, you mentioned.

I always used to change air and fuel filters on my old car at 16k, as recommended by the manufacturer.

With the Fabia vRS they recommend 40k for both !

I looked at the air filter (16k) and it was grey with black. Vacuumed it out - as mentioned by some. Wasn't happy so bought a new one.

Similarly, will be replacing the fuel filter at 20k instead of the 40k recommendation.

Oh, worse note - what's the oil consumption like ?

I believe the petrol 1.4s are prone to piston ring trouble at 60k (from what I've seen on the forum).

I was worried about the piston rings from glancing through the forums, but after further readings the pistion ring trouble is with the newer 2000 1.4, the 16v not my 8v mpi. And we would have noticed if it was the piston rings would have heard it and noticed the extra vibration. No excessive oil consumption anyway. Yeah like i say i hope i change the fuel filter (when it stops ruddy raining) and all will be well. Its done 16k since ive had it so good knows how long the current filter has been in, why i thought it would be a good idea to change it.

Piston rings - I'm wrong again. Just shoot me.

Might also be a good idea to do a Google for rolling resistance of tyres - see what types of penalty are involved from tyre to tyre.

I think I've seen past claims for some Michelins of the order of 3% improvement (Energy etc) - so I doubt the Falkens penalising you as much as you are losing now.

But, going off everything I've said so far, I could be wrong !

Best of luck sorting it - really nags at you when something is wrong, like a vulture pecking at your neck.