Pretty damn fine fuel economy
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  1. #1
    Fellow Frogger! vanderaj's Avatar
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    Default Pretty damn fine fuel economy

    I've just got back from a week up in deepest darkest Leeton, NSW. On the trip back, I managed to get my best ever fuel economy - 6.75 l/100 km, even though I didn't make any particular effort to drive in an efficient manner or even turn off climate control (it was 38C... I had a nice 22C in the car).

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    For example, let's just say that I made it to the NSW-Vic border a few minutes before I should have. Very impressive for an automatic, loaded with stuff for a week's travel, 110ish speeds most of the way, climate on, and city traffic for the last 40 km.

    Andrew

  2. #2
    Good Sport danielsydney's Avatar
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    Andrew is this in a C3 or another Citroen??

  3. #3
    Fellow Frogger! AxGT's Avatar
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    I got an average 6.2 L/ 100K driving to and from Maleny - pretty crazy

  4. #4
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    Whilst those figures are good, it shows how much fuel an auto transmission wastes. Our manual C3 regularly achieves 5L/100km on the highway. Fully loaded, on Tassie roads, the highest we've seen is 5.7L/100.

    Derek

  5. #5
    Sense Pug307's Avatar
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    It's strange that there is such a large difference in fuel economy between the auto & manual discussed here, on paper there is only 0.2l/100km difference. Given that real life highway driving conditions translate to a 34% increase on book figures, that's still only a difference of 0.27l/100km which is a very small difference. Andrew, are your figures from the trip computer or manually computed, as Derek's are manually done, off the top of my head. This could explain some of the difference.

    It does seem a bit odd to me, as the AL 4 auto gearbox has torque converter lockup in second, third and fourth gears. With an unlocked torque converter, some of the engine's drive is wasted in the torque converter's fluid coupling through heat for example. However, at cruising speeds, the torque converter is locked up - eliminating that waste. In addition, the auto C3 has taller gearing in top gear than the manual (it's few hundred rpm at cruising speed).

    Book figures show a much larger difference between auto & manual in the C3 for the city cycle. 6.8l vs 8.0l/100km (actually that city figure is the same as the 307 1.6 auto). This is understandable, given the efficiency losses through the torque converter which is more likely to be unlocked in stop start driving.

    In some cases (generally the exception to the norm), auto gearboxes have better fuel efficiency than manual ones on the country cycle (chiefly due to gearing, I suspect - autos are generaly taller geared to offset against inferior fuel economy). Do auto gearboxes have greater internal friction or something like that, leading to the higher highway fuel consumption figures?

    Peugeot 307 XS 1.6
    Aussiefrogged in MEL, PER, SYD, BNE & ADL.
    Rendezvous Adelaide 2005

  6. #6
    Fellow Frogger! vanderaj's Avatar
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    It's the C3 Exclusive Panoramique 1.4 auto. At 110 km/h, the engine is doing a neat 3000 rpm, around 2700 rpm at 100 km/h.

    Um, I made absolutely no effort to constrain fuel burn - I had climate on, and I drove at the speed limit most of the way except where I could see for miles and there were no cars ahead or behind me ... and then I went a bit faster. However, once I hit the Victorian border, I kept to the speed limit. I saw the only police car of my trip just after crossing the border, plus more to the point, there was traffic in both directions from the border to Shepparton and there's absolutely no point in going faster than the speed limit on the (better than autobahn quality) Hume freeway in Victoria as you'll get a ticket or two.

    Before leaving, I ensured the tyres were correctly inflated and oil was at the right level (it doesn't seem to burn any). Beyond that, I made no effort to baby the car.

    I'm sure if I kept to speed limits, baby it over the hills and let off coming down the other side, I'd do better. I manage 7.2 - 7.5 l/100 km to and from work, which is 25 km of 0-25 km/h stop start driving going to work and 25 km of 100 km/h freeway driving home.

    I measure my fuel economy by always filling to the third time the pump clicks off, and using the litres of fuel used and the odometer's trip distance (which has a decimal digit). I tend to use Shell Optimax. For some reason my average speed and average fuel economy settings in the trip computer are wrong (it reckons I do 1 km/h on average), so I don't necessarily believe the trip computer.

    Andrew

  7. #7
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    wow thats pretty darn good!!!! petrol over here in scotland is much more expensive i hear as well! u lucky bums

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