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I bow to Number Cruncher's superior knowledge! I was going to suggest letting the whole set up run for 2 or 3 months, 4 or 5 tanks full ,to get a better result. I now see that this would be a BAD thing! I don't know what my computer is like (307), I just look at it and observe that it records a consumption. As with speedos, I guess there is a error. Speedos always over read becuase they are not allowed under-read. Perhaps car manufacturers put a little factor of over-reading into the fuel computers to make you feel better about the car? In the end you use the car, you have to fill it up now and again and if it is a small engine and/or a diesel it won't be quite so often as a petrol. Certainly the computer 'learns'. I had my ECU reset to cure some problem and the indicated range for a full tank showed as 250 miles, normal is 600+. I went straight back in to the service dept and they said that it would recalculate according my driving. Sure enough, over the next 2 days the range went up as the tank contents came down!
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>>I was going to suggest letting the whole set up run for 2 or 3 months, 4 or 5 tanks full ,to get a better result.
I think if you are recording the total amount you put into the tank, and the total number of miles covered, then you probably are going to get a more reliable result if you repeat the process over a number of tankfuls. Even with an error of, say, 50 ml for each tank fill of about 30 litres, and the error in the odometer, you aren't going to be a long way from the truth.
Number_Cruncher
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Should've explained, she's been recording the data at each fill-up across the last few months, along with the mileage read from the trip computer, before resetting it and the mpg figure to zero, and has just spent the time converting the numbers into mpg. These fit in the range given above!
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Mine does exactly the same - trip MPG is optimistic by a shade over 5 mpg. Driven briskly on my commute and getting stuck in occasional jams it does about 43-44 mpg; on longer motorway runs I can get about 48 mpg. I'm pretty pleased with that because it is a fairly heavy car and I use the a/c all the time and the "transient overboost" facility regularly, and it is still 7-10 mpg more than the 1.6 Honda Civic it replaced.
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Ah! Just thought of something, we constantly have the automatic climate control on! I would imagine this is something that could affect the mpg to this degree?
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There are lots of previous posts on TDCi fuel economy so its worth doing a search and having a read. Mine (130 Ghia Estate)has never been particularly economical. I tend to drive mine reasonably hard, and return about 42 with climate on (brim and measure method). Towing a trailer with boat, it dips to 36. The trip is usually a tadge optimistic.
Some people seem to get lots more, and speak of over 50 as a matter of routine. I have only ever got the trip to read over 50 by travelling down a dual carriageway at 65-70mph, and feathering the throttle. I once got a 60+ reading doing this. But this isn't normal driving for me! It also defeats the object of the 130bhp which I like to use.
Its a great car, with a punchy engine, great handling and, I think extremely well put together. The fuel economy just isn't its No1selling point!
Splodgeface
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I know the fuel economy isn't the number one selling point, but it was the selling point as to why she bought it. It was the only car in the class where the steering gave some of the feel she'd had from her Celica - she doesn't like cars where she can't actually feel anything through the steering as she finds it disconcerting! She settled on this class of car (diesel) because she does 30,000 miles/year and thought it would be far more economical than the Celica (36-38mpg) she was going to replace with another...lol, guess some things just don't work out like they're planned!
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Mine does exactly the same - trip MPG is optimistic by a shade over 5 mpg. Driven briskly on my commute and getting stuck in occasional jams it does about 43-44 mpg; on longer motorway runs I can get about 48 mpg. I'm pretty pleased with that because it is a fairly heavy car and I use the a/c all the time and the "transient overboost" facility regularly, and it is still 7-10 mpg more than the 1.6 Honda Civic it replaced.
Just to give you an idea of the progress that represents, my 1.8TD mk2 is probably 150kg lighter, has 40 bhp, yet cannot beat those economy figures.
Amazing things, modern diesels.
Cheers
DP
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Sorry, should read 40 bhp less, although with a full load and the air-con on, it feels like 40 bhp! :-)
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Just to give you an idea of the progress that represents, my 1.8TD mk2 is probably 150kg lighter, has 40 bhp, yet cannot beat those economy figures. Amazing things, modern diesels.
Good points, you could also say not much more than half as much torque.
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I should have added to my previous post that all of this is achieved whilst delivering the sort of mid-range acceleration that my Civic, capable though it was, wouldn't have achieved downhill with a following wind!
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My Ghia X 130 easily achieves 48 to 50 mpg, I have measured it over 109,000 miles, not based on the trip reading rather litres purchased v miles driven.
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An elementary starting point if you want to be really accurate would be to test the odometer accuracy over a long run, by measuring the distance on a map.
I suppose it would also be possible to calibrate the garage pump by dispensing a stated 5 litres into a weighed can, and then re-weighing. Take its temperature too.
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Or using the distance markers on a motorway. I think these would be better than map figures but you would need a passenger to do the counting and identifying of the markers!
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Any walking style GPS unit will be able to give you an incredibly accurate distance reading, assuming you don't go through any tunnels of course...
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Gordon M I have got one of these, a Garmin E Trex. It will measure distance A to B, obviously. But, will it measure the distance from A to B along the route that you take ie give you the distance you walked, along an indirect route, perhaps avoiding lakes or huge obstruction that force you off the straight line route?
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My GPS, a Garmin Foretrex 100, has an odometer feature that will give you your actual distance moved. You also have the option of downloading the track information into MemoryMap or similar, where you can get distance, ascent, descent, speed at any particular point, average speed etc.
On mine, and on the only other Garmin GPS I've tried, you can select this info on the 'trip computer' screen, where there are 6-8 slots and a choice of about 30 metrics you could display.
HTH
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Thanks Gordon. I bought mine to amuse my grandchildren, mostly. E Terx is very much bottom of the range but, as ever, I will read the book! Thanks for your input!
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Mine's a 55 Reg 130 TDCi Mondeo Zetec, Euro III, on my very short commute to work (3 miles each way), I got 41.5 mpg in cooler weather and 44 mpg in warm. This was worked out brim to brim, the trip showing on over optimistic reading of 3 mpg above this in each case. However on the motorway, if I cruise between 60-70 mph, the trip will show 58-61 mpg (warm weather) and on the A roads at varying speeds it usually shows 55-57 mpg. So basically the worst I've had is 41.5mpg (calculated) and the best Ive had is 58 mpg (trip-3 mpg). I can get the trip to read 99.9 mpg by resetting it after I fill up, because the garage is at the top of a hill in a 30 mph limit, after setting off from the garage I don't need to touch the pedal for about 0.5 miles.
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