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Corsa D 1.3 CDTI Poor Fuel Economy

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  • [Corsa D] Corsa D 1.3 CDTI Poor Fuel Economy

    Evening all,

    About 2 months ago I purchased a 2013 Corsa D 1.3 CDTI SXI (95bhp Ecoflex version) with 55000 miles on the clock. I purchased the car expecting MPG of at least 55+, given the fact that the Honest John real mpg statistic is 63+ and the official combined figure is 64.2. Over the 1700 miles I've driven the car since early November, most fill-ups have seen a brim-to-brim average of around 49MPG. The trip computer almost always shows 56.5MPG at the point of fill-up so there quite a discrepancy between the real and indicated figures. (As a side note, is it normal for the trip computer average MPG readout to go up in increments of 0.9MPG?!)

    My driving is roughly about 50% on motorways at ~75 mph and the other 50% is divided mostly town driving with the longer occasional A/B road trip. During an average week I do a 50 mile motorway run on a Monday and then have a 2.5 mile commute morning and evening from cold for the rest of the week until Friday when I do 50 miles back up the motorway. I appreciate the short cold journeys would have an impact, but I wouldn't have thought they could change the figure so drastically. Also, being only 19, my right foot is probably a tad heavier than some, but not to any great extent.

    I was just wondering if this is normal, or whether there could be some underlying problem with the car that could be causing it to drink more fuel than it should. It could just be that my expectations are two high. (i.e - having 2 1.4 D4D Yaris in the family doing 58+MPG under similar conditions)

    Thanks in advance,

  • #2
    Hi Welcome to the forum.

    As the current owner of both a corsa 1.3 cdti (75bhp) and a diesel Yaris i should be ideally placed to answer your question. Unfortunately they are used under very different circumstances and I dont closely monitor mpg. Yaris mostly fast motorway, Corsa mostly gentle ,fairly long ,runs on a and b roads ,not much town. I think I get about 58-60 mpg on the yaris when used gently. Not quite as good as my earlier, lighter, yaris which regularly gave 65mpg . |With the Corsa I think 55 mpg is more typical. But thats me. I am a very gentle driver who thinks having to brake can be a failure to anticipate. If you've ever watched a constant fuel consumption display you will be appalled at just how much fuel a car guzzles when it has to regain speed. . I've seen it as low as 5 mpg on a jeep. With your short cold journeys and a young right foot 49 mpg may not be too far off the mark.The corsa is a bigger,heavier, car than the yaris and this can make a surprising amount of difference.

    But there are some things that may help. Make sure the car has been properly serviced.

    Put a bottle of diesel fuel injector cleaner in the tank .Dirty injectors can cause poor fuel atomisation which can affect mpg. Chose a cleaner designed to give cleaning results in one dose.Some others are only intended to keep already clean injectors clean when used in every tankful.

    Check your tyre pressures. Manufacturers fanciful mpg figures are based on the tyres being at the recommended pressure, which is often quite high to improve their results. Pressures that may have been set in hot summer temperature (or set low for a more comfortable ride) may be too low for winter. Ideally compare more than one pressure gauge as they can vary quite a bit.

    Also your tyres might affect mpg. Some brands have much more rolling resistance than others. The pirelli cinturato P6's I foolishly put on the front of my Yaris have a dreadful fuel consumption rating despite allegedly being eco tyres. - class E when most decent tyres are B . This might lose you a mpg or so.

    Also check that your brakes are not binding a bit. See how readily the car rolls at slow speeds with the clutch in or in neutral.
    Last edited by Bugman; 12-01-2019, 08:11 AM.


    • #3
      I have known people who have stripped every 'unnecessary' item out of the car to reduce its weight and so improve mpg. this has included taking out the passenger seats and the spare wheel.
      At the other end of the scale, there are people like myself who carry tools and just about everything but the kitchen sink.
      It would be interesting to compare fuel figures for these two extremes.

      Does your car perform as well as you would expect? There is a chance that there is some mechanical problem that prevents better performance. Bugman mentions binding brakes, which are not an uncommon problem. It is also orth making sure that the clutch isn't slipping (If the revs go up when you accelerate, but the road speed dose not increase proportionally, the clutch is probably slipping)
      Is there any signs of BLACK exhaust smoke? This could indicate that too much fuel is entering the engine, or that it is receiving too little air (due to a blocked air cleaner for example.)

      If the car is in good order and well maintained, the problem is probably due to those short journeys, and as you say yourself, the size of your right foot.



      • #4

        Thanks for the input.

        The car has been serviced in the last 2000 miles so should be in good order. I also checked the tyres a couple of weeks back and they were down about 5psi on each corner which wouldn't have helped, but I haven't had a full tank of fuel since to measure the difference.

        The performance seems to be OK, although this is only my second car, my first being a 1.0 petrol Aygo so this feels a bit like a rocket in comparison! I haven't noticed any symptoms of binding brakes or slipping clutch, but I haven't really checked so I'll have a look at that.

        I'll try the injector cleaner in the next tank of fuel and see if that helps. Failing that, it looks like I might need to try and drive a bit more economically!!



        • #5
          Dont expect miracles from the injector cleaners . Makers claim 5% improvement is possible, so you may get a couple of mpg. But there may be no improvment and sometimes you may only notice the car is running better some time later.

          Unless there really is something wrong mechanically how you drive is likely to give the biggest gains, and its good you realise that at 19. Both throttle and braking.

          When i was your age I couldnt afford to improve the car so decided to improve my driving instead. I bought a copy of "Roadcraft" . This is actually the official Police drivers Manual but it is available to the public. (I think you can still get it, but probably updated over the ,erm, few years since))

          It was a revelation. You'd expect the police to tell you to drive like your granny, but they actually teach you how to drive quickly, more safely. And more smoothly . Well maybe how police can drive quickly, while you should keep normal speeds and benefit from a bigger safety margin. - yeah well.

          But it enlightened me on how much of the Highway code is simplified for novices to avoid information overload. Heres is the police telling you that with advanced levels of observation and hazard awareness its not always wrong to,for instance, straight line roundabouts and bends, or even drive on the 'wrong' side of the road for a better view ahead. The essence of advanced driving is to look and plan well ahead. Typically MUCH further ahead than most people do. This avoids much of the late braking and need to build up speed again typical of many drivers and saves a LOT of fuel.. An advanced driver can maintain higher speeds while still looking relaxed.

          I later passed the IAM test. Even today I often leave drivers of much faster cars for dead on the wiggly wogglies. Unfortunately they hate being bested by a lowly diesel and may thrash the nuts off their car and drive beyond their skills to try and catch up. So I have to moderate my fun.

          But there is no need to buy Roadcraft. Here is a link to one of many advanced driving tutorials by Reg Local. I think he is an ex Police advanced driver. I certainly looks like the stuff I learned from Roadcraft. They may help you with both safety and smoother fuel saving driving without sacrificing too much youthful enthusiasm.


          • #6
            Thanks. I'll certainly look into that advanced driving. It must be very useful to be able to drive to that standard.