I've recently bought an 08 Skoda Octavia 1.9TDI Elegance Estate and noticed the current fuel consumption figure on the dash varies widely from second to second from approx 15mpg to 100mpg plus at constant speed.The average fuel consumption figures appear to be correct for the type of driving I am doing at the time but I am not sure the current mpg figures indicate some kind of sensor failure???

I know it's pretty minor but wonder if it indicates some kind of pending more serious fault?

Thanks

Martin

Could just be that the trip computer is goosed, I would expect the average mpg figure to be wrong if there was a sensor out of whack.. Try disconnecting the negative lead on the battery for 10-15 minutes to see if it totally resets things. Does it still go nuts if the cruise control is on?

Failing that, pop in and speak to someone at your dealer.

Don't panic !!! there are 2 settings, 1 displays your mileage as you are actually driving,,varies hugely, and another to show your average mileage..check your handbook, and all will be sorted

The actual consumption does vary widely, on my 2.0tdi I see figures between 10mpg and more than 100mpg when viewing the instantaneous figure.

Even on a "level" road with the cruise control the current consumption will vary hugely.

On a long gently undulating 50mph section on my way to work, mine varies between 45 and "---" (ie 200mpg+)

try the pressing the button to change the mpg display to the next one that has a 1 and a small circle with a line through it. thats the one you want.

I for one don't see massive variations when looking at the instantaneous consumption figure, if driving on the straight and level the figures don't vary that much. You need to be thrashing the *** off the car to see the MPG drop to 15 when on the move. If I'm driving along a level road at a steady 60mph the instantaneous figure is normally around 55mpg, it doesn't vary like the OP is suggesting.

I for one

Yours is more likely broken then - I've driven probably 2 dozen different Octavias, and a load of Passats, Vectras, and all manner of vehicles, and all of them the instant consumption goes between 8mpg and --- or 999.9mpg when on cruise - depending on gradient of slopes and even direction of wind.

I for one don't see massive variations when looking at the instantaneous consumption figure, if driving on the straight and level the figures don't vary that much. You need to be thrashing the *** off the car to see the MPG drop to 15 when on the move. If I'm driving along a level road at a steady 60mph the instantaneous figure is normally around 55mpg, it doesn't vary like the OP is suggesting.

as said your car is either magic or broken, as above my octavia, brothers ibiza, dads astra, my mates 328 and swmbo's vectra vary wildly when watching instantaneous

infact i was driving swmbo's vectra(3.2 gsi) on sunday from oxford to banbury along the old road at 50mph on cruise with 3 adult passengers and even on fairly flat roads the mpg was varying between about 20mpg and 50mpg without any hills in sight.

That seems about right for instantaneous fuel consumption. It certainly makes you aware that even the slightest unnecessary movement of the accelerator can markedly affect the fuel consumption.

Cruise control keeps you at a constant speed and gets you to that speed as soon as it can, it will make your fuel economy worse when driving in hilly areas.

Yup, instant does that. Average (with line through) should be fairly stable, but will drop if you boot it.

i agree with benji, i drive for a living and can watch the lorry mpg go from 1mpg to 200 mpg just travelling down the road at 30mph.

My car is the same, but stick it on the circle with a line through it and its average for that journey and is better imho.

The instant MPG readout is pretty useless really as it varies so much depending on gradient, throtle position etc. It would be more sensible if it showed the average of, say, the last 10 seconds. That would at least stop the reading fluctuating so massively.

Yes my car is obviously magic then.

Funny that my current Octavia TDI and my last 2 Octavia TDIs have all kept a fairly stable instant readout on a level road at a steady 60mph, it certainly doesnt fluctuate from 10 to 200mpg in a second unless foot to the floor or foot off the gas pedal, when cruise is enabled on the motorway the instant will fluctutate between say 30 and 65 but never silly stuff like 10 or 100.

The instant MPG readout is pretty useless really as it varies so much depending on gradient, throtle position etc. It would be more sensible if it showed the average of, say, the last 10 seconds. That would at least stop the reading fluctuating so massively.

it isnt too bad if you trying to be economical as you can aim to keep the mpg over a certain level. i often use the instant one on the way to work to try and improve my mpg by trying to keep the instant above a certain figure.

Yes my car is obviously magic then.

Funny that my current Octavia TDI and my last 2 Octavia TDIs have all kept a fairly stable instant readout on a level road at a steady 60mph, it certainly doesnt fluctuate from 10 to 200mpg in a second unless foot to the floor or foot off the gas pedal, when cruise is enabled on the motorway the instant will fluctutate between say 30 and 65 but never silly stuff like 10 or 100.

try sticking it on instantaneous and driving down a road with just gentle inclines and decents with cruise on, i'm not talking hills just not dead flat. swmbo's vectra was ranging from 10 to 999.9mpg with cruise set to 50mph on only mildly undulating roads.

when it is set to cruise the car is telling itself it needs to maintain (and for arguement sake we will use 50mph). Therefore when it comes to a steep hill and is slowing fast the car will pump more and more fuel in to try and maintain the speed of 50. when it comes down the hill it doesnt need any fuel to maintain the speed so the mpg will read off the clock. Because the car cannot see bends and slight dips etc it will keep pumping and not pumping fuel into the engine to maintain the speed thus the erratic jumps. If you were to get up to speed and read the road ahead you could possibly get the instantaneous reading to stay pretty much more level than cruise can as you can let off accelerator and add it as and when you see fit. a small hill might mean you can roll up it well knowing that coming down the other side which is steeper means less fuel is needed.

Thanks for all the replies. The average mpg seems about right for the type of driving, the only time the instantaneous fuel consumption seems to stay fairly constant is when the cruise control is on and driving on a level straight road (makes sense I guess). As one of the posts suggested.

I imagine the fuel consumption at any instant varies widely but regularly hits the same mpg which means the cumulative average displays correctly. As mentioned here the instantaneous mpg would be more useful if it average over 10-20 secs.

Thanks again for everyone's posts, good to know it's not an expensive computer going haywire.

Thanks

Martin