I am not happy with the fuel consumption of my 1.6 CR Fabia. I bought it when it was about 15 months old and the initial fuel consumption was 58mpg. I tried several different brands of fuel and it didn't like the super-diesels so I stuck to standard Shell.

Through last autumn and winter the fuel consumption has increased. Before Christmas it was rarely above 50 mpg and recently this has dropped to about 48. These figures are for a car used mainly on shopping trips (20 mile round trip) round rural Norfolk with little town driving.

On Wednesday, I did a normal 40 mile tour round the county and got about 48 mpg (figures from the computer rather than for a refill). The outside temperature was 12 degrees. Yesterday I did a very similar trip with a bit more town driving and got 60!! The only difference was that the outside temperature was 16 degrees.

Same driver, same weight in the car. So is the car hyper-sensitive to outside temperature?

I am anoyed that the car has no engine temperature gauge other than the blue cold-engine warning light. I would like to have water and oil temperature as well as oil and boost pressures. However, there doesn't seem to be any simple and straightforward way of getting this information (if anyone here knows differently, I would be very grateful for the information). So I am reluctant to fit covers to the 2 front grills but with these changes in fuel consumption it is very tempting to run a test.

I am an old slow driver. On Norfolk's mainly single carriageway rural roads it is difficult to be anything else. Therefore the car rarely gets a fast run or even exceeds 60 mph.The only hard driving comes when overtaking a slow car or lorry which means about 3 seconds in 3rd from 40 to 65. As a result, it often idles badly either from dirty injectors or a semi-blocked particle filter. However, a hurried trip to the local hospital a week ago seems to have cleaned these at least for the time being.

Sorry if this sounds like a rant. I am just trying to understand this funny little car. I hope to live with it for at least the next 10 years and probably more if all goes well (with me as well as the machine!!). Comments from the dealers that 'all cars behave differently' doesn't wash with a modern computer managed mass produced cars like it might have done with hand built specialist cars of earlier times (Aston Martins, Ferraris, etc of the 1950s and 60s).

I am pretty sure the computer system is sensitive to the brand and grade of fuel used. Hence the decision to stick to one rather than use a mixture. But what else is it sensitive to?

I doubt its that sensitive to outside temps.... as you mentioned about modern computer controlled systems, once the car is up to temp, the relevant systems will keep the engine temps the same, regardless of what its doing outside....

you may notice a few mpg difference between say a summer of 20+C and a following winter of -16.... but in what you are describing, and by so much....

there must be something different thats happening....

just a few tips on high MPG drivivng....

1) dont be afraid to use full throttle, an engine is most efficient of full throttle (and as you say it will help to "clean " things....)

2) dont brake..... this is the most important thing... everytime you brake, you waste fuel that you have used to get up to speed.... (I can make it my usual 19 mile commute to work in my vRS and get 48 mpg, and I dont brake until I get into the town I'm heading for!) for example.... you can back off MUCH further away from roundabouts than you think... try it! try releasing the the throttle far enough away , so that when you change to 3rd or 2nd at the next roundabout, you dont need to brake unless anything is comming....or if thats not the sort of road in raural Norfolk, try the same with the bends on the country roads... just try backing off far enough away so you dont brake when you arrive at the ben...

remember on "ovverun" when you are off the throttle and in gear slowing down, the ECU will cut fuel to the engine...

any more of an analysis would require more information

good luck!

What he said lol. That's pretty much what you should do to drive economically

What they say,

& my pennies worth.

I have run Fiats Qubo's & Peugeot Bipper's for work, Diesels with Dualogic gearboxes.

The none DPF Bipper did the same fuel consumption as the Qubo, anything from 40-65 mpg easily.

The Qubo could go into DPF regeneration & the MPG would drop to 25 mpg or so.

Since the vehicle was shared, i could get in it after a few days of someone else driving it, and be pottering around town and then bloody hell i go out the road & the thing is using up diesel like it is washer fluid.

If you have a DPF filter then look at your Fuel consumption in terms of weekly averages not daily maybe.

Outside ambient temp here today was 3.5 degrees celcius, i dove 10 miles and my engine oil only got to 51 degrees celcius before i stopped.

Yesterday it was snowing but 6 degrees celcius & the oil was 76 degress when i had done the same journey.

Last week when it was 16 degrees celcius my oil was up to 85 degrees after about 5 miles and i was off up the road giving it more welly.

Ambient air temp of course effects how long it talkes to get the Engine coolant up to running temp and then how long it takes to heat the engine oil.

Often this has less effect on a diesel engine than on a petrol engine.

Snowing here today in Northern Scotland.

george

PS.

Never even mentioned, the Winter, Start the car, defrost it, heated rear screen on, heated mirrors & Dipped beam, heater running and slower for getting the thermostat open and the engine coolant hot then the engine oil.

Alternator getting going and all more fuel.

But driving slower so maybe not more fuel.

Summer, jump in car & drive off with just the radio going and maybe DLR's , might use more fuel as you are driving a little faster quicker.

I Had a Hyundai i30 TD Auto for a year and watched the fuel closely.

Tried Shell V power & BP diesel etc, and it like the dearer stuff.

35 mpg at worst and about 55mpg -60 quite easily.

Fast enough car with loads of torque & faster when needing to climb a hill fast and someone up your jacksy when you switched on the A/C and the Alternator kicked up oddly.

(it had an effect on the Autobox and made it react like a sport button, really!!)

Almost no engine breaking and cr4p in poor weather with ECO tyres.

Difficult to get it moving in snow or ice other than in reverse, and going forward when the Turbo kicked in, you had to watch it for wanting to go off road.

Best fuel consumption was at about 0 to 8 degree celcius outside temp.

Was that the big Intercooler at its happiest, i thing it was.

Same drive and same road at about 18 degrees celcius, no A/C on or anything and the fuel consumption and the revs were all different and the car was not so smooth.

george

Edited 18 May, 201214 yr by sk4gw

By the sounds of things you may not be having ideal driving conditions for keeping the DPF clear, and as above, it's going into regeneration, which hammers the efficiency.

I am starting to get better MPG mainly because I do mostly motorway driving and can keep the DPF clean.

Also, if you are doing town driving, don't be trying to get up the gears quickly, these engines don't like it. At 30mph in my CR, I'm only just in third (I do have longer gear ratios) and this is about 1600-1700RPM, and the lowest I let the RPM get in any gear is ~1500RPM.

I also notice the fuel consumption is VERY sensitive to outside air temperature.

Of course there are many other factors that change from winter to summer. sk4gw pointed out a few of them. Others include winter tyres, winter diesel and more traffic. In warm weather the stop-start starts working within 2 minutes of leaving home. In cold weather, much longer - and never when it's really cold.

But even taking all the rest into account the trip computer says we use a lot more fuel on the same school run when its +5C than when its +20C. Of course, the standard fuel consumption tests are performed at +20C, so I suspect that the whole car is very highly optimised to get good figures in the lab, rather than the real world.

Or could it be that the trip computer calibration is temperature sensitive?