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Ratho1

Fuel Consumption

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I don't want to get too obsessed with fuel consumption but I've just refilled my tank and returned an average figure of 48.3 mpg. This compares with a trip computer average of 55 mpg which I really thought that I was getting. Several long runs had returned in excess of 60 mpg along with the poorer returns from short journeys and based on my first fill up I thought that the computer read outs were reasonably OK as a previous fill up had given 53 mpg against a trip computer value of 55 mpg.

I'm obviously troubled by two things, the high fuel consumption and the big discrepancy between real and computed value.

Someone on a previous discussion on mpg had mentioned that fuel consumption would rise between summer and winter. It has been my experience that although it does rise a little due to cold starts etc. there is not a lot of difference. If I am to expect a much bigger seasonal variation with a hybrid can someone explain why ? I thought that an Atkinson engine would smooth out this variation but maybe I am wrong.

P.S. It really is an enjoyable driving experience, if not as economical as anticipated.

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I don't think cold starts affect the consumption in winter, it is more a case of you having the heater on and the car having to do more to keep you warm. Some people switch the heater off when they stop to let the engine stop - I sometimes do but not all the time. This was also the case in the Prius I had before the Auris

The computed display in my car seems to always show 3 mpg better than the actual consumption but I don't suppose it justifies the expense of F1 telemetry. I think it is more of a guide than an actual value. Had many cars with such a display and they are always optimistic.

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I agree these MPG displays are only a guide, they all read optimistically, but this one in my Auris hybrid is the most inaccurate I've had, it shows about 62 MPG per tank, but is actually calculated to about 57 MPG, still not bad for an automatic car.

The weather has an effect, cold, wet and wind all reduce the MPG, but the biggest effect is how many short journeys you do, short runs really knock a hole in the MPG average, but I suppose that's true of all cars not just hybrids, it's just that hybrids are perceived to be very fuel efficient and many people buy them expecting too much.

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I had anticipated that all of the factors that affect petrol/diesel cars would apply equally to hybrids in winter and certainly short runs hammer the figures but in my current case I actually had more long runs than short compared with the first tank full, hence my surprise. My other surprise was the big (14%) discrepancy between actual and computer figures for mpg. As both Kevin and Peter have said a gap of 3-5 mpg or 10% is not uncommon, but 14% ? That is poor technology.

They say that we should learn to drive these cars in a different way. Perhaps I should try pushing for a while. :driving:

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Before you start pushing your car I should try a few more calculated fuel up's, it's difficult to ensure you fill your tank to the same level every time, some pumps knock off at different levels, which could account for your 14% discrepancy.

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Very true Kevin. I guess I am just too impatient sometimes. In any case it's so cold out there my hands would probably stick to the boot lid.

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