Anyone else noticed this? It's on my daughter's little 1.1L 3 cyl Mitsubishi Colt.
Driving from her house to our's on open rural roads she'd normally be nudging 50MPG on the trip display. Now it's very low 40's. She's getting similarly low results on other regular trips.
Of course, this co-incides not only with the cold weather but also with having the front discs & pads changed. I know that's most unlikely to affect things but I did check and the car rolls easily, but she said that she feels she's having to "push" the car more. It seems to drive well to me, although it does lose speed quickly on the over-run, but coasts OK. However I don't drive it regularly enough to be able to make a comparison.
If anything, doesn't colder air allow the engine to produce more power - so it should feel easier to drive in cooler weather?
I checked the tyre pressures and made sure the engine had oil in it!
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Our mk1 1.0 Yaris's TC used to consistently read 43mpg in winter and 47mpg in summer.
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Have you jacked it up and checked each wheel for drag?
Maybe it needs a trip to diagnostics to make sure that all sensors are working properly. The engine should pull well in damp, cold weather.
Last edited by: corax on Tue 6 Nov 12 at 16:55
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Forget what the trip computer says, and calculate the fuel consumption in a more realistic way such as over a period of one month minimum. Even doing that, you'll find that the consumption will variy significantly from one month to another, depending on the journeys, driving style, weather etc. My experience of trip computers (coupled with religious records of calculated fuel consumption) is that they should be treated as toys.
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How long is her average journey?
It'll effectively be using enrichment (think choke) for longer as a result of being colder and also because she's probably taking more heat out of the engine with the heater.
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>>Forget what the trip computer says, and calculate the fuel consumption in a more realistic way
I believe the point is not what the trip computer says, but that what it says has changed.
All trips vary, the temperatures vary, dirving styles and traffic vary, everything varies, but a +/- 20% change in trip computer read out bears thinking about.
I'd do as Corax suggested; jack it up and spin the wheels. Coincidences happen, but not that often.
Last edited by: No FM2R on Tue 6 Nov 12 at 17:16
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>> I believe the point is not what the trip computer says, but that what it
>> says has changed.
>>
Correct.
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>> I'd do as Corax suggested; jack it up and spin the wheels. Coincidences happen, but
>> not that often.
>>
Will the front's will spin freely anyway as it's FWD? I could roll it without undue effort - especially compared to wifey's Jazz, I have to move that away from the garage now and again and it's everything I can do to move it.
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I would personally think the difference is weather related. But it's worth checking the wheels.
There may be some resistance and you'd need to jack it up to spin the wheels. I don't follow your logic about the front wheel's spinning freely because it's FWD. In fact with that logic it's the rears on a FWD car that would spin freely.
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>> I don't follow your logic about the front wheel's spinning freely because it's FWD.
>>
I'm wondering if they will spin freely when jacked up due to the drive-shafts etc.
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>>Will the front's will spin freely anyway as it's FWD
They will not freewheel as such as they are carrying the weight of a drive shaft. But if you roll the wheel half a turn or so forward and then backward, you will be able to feel if it is binding.
Is this MPG the rolling MPG or Trip MPG? Its not something as simply as a mechanic thrashing the car when "testing" the brakes, is it?
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>> Is this MPG the rolling MPG or Trip MPG?
It's trip MPG - it resets after 3hrs. Although thinking about it, I wonder if it could be incrementally resetting to a lower and lower start point each time.
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First thing I would do is measure it brim to brim. Already said by others above.
My VW diesel (170PS) will be down on mpg for a lot of the driving I do local now. But at the weekend and about 460 mile round trip it was back higher than ever... then again I've not quite done 10000 miles in 12 months! That's a record low for me.
I can see me going petrol turbo next time. The emissions on a Golf GTi petrol were a bit too high and would have cost me more than this car per month. Which is bizarre since mine is a lot better equipped and more expensive. But that's residuals and BIK for you. The next Golf GTi (petrol) has lower emissions.
Anyway work it out brim to brim and report back.
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Bathtub Tom makes a good point - the car will be running for much longer with enrichment, and it will take longer for the car to switch into closed loop fuelling mode. Does the engine management lamp work?
It's a good plan to make sure the wheels all rotate without too much drag - the brake pads do always just touch, but, shouldn't drag significantly. Checking tyre pressures is always worth doing.
As I think Mark mentioned, it's worth making sure exactly what work was done - that might give a clue.
Again, I think I'm echoing Mark's point, although I wouldn't trust the absolute figures displayed on any dashboard gimmick, I would take the change in the numbers displayed seriously.
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A drive up the dual carriageway followed by a gentle stop in a layby on handbrake alone, then feel the front brake discs (careful) will soon show if any drag.
Worth checking the obvious, air filter and its intake in case somethings got sucked in.
Depending how far North you are i don't think its got cold enough to make much difference to fuel consumption yet, my LPG still switches over after a couple of minutes.
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>> A drive up the dual carriageway followed by a gentle stop in a layby on
>> handbrake alone, then feel the front brake discs (careful) will soon show if any drag.
>>
I haven't done that, but I did do a straight line test - it ran as remarkably true as it's always done. I'll try as you suggest at the weekend.
>> Worth checking the obvious, air filter and its intake in case somethings got sucked in.
>>
That's a good point, thanks.
>> Depending how far North you are i don't think its got cold enough to make
>> much difference to fuel consumption yet, my LPG still switches over after a couple of
>> minutes.
>>
That was my thought too - we've had a couple of frosty mornings, but most days it's not been that cold. I would have thought the little engine would warm up pretty quick.
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>> Does the engine management lamp work?
>>
Yep.
>> Again, I think I'm echoing Mark's point, although I wouldn't trust the absolute figures displayed
>> on any dashboard gimmick, I would take the change in the numbers displayed seriously.
>>
She mentioned today on refilling the car that range was under 400 miles and it's normally just under 500. I think she thought (although she wouldn't say) it might be down to me filling it with petrol at Tesco, the car is normally only fed on Shell. However she's refilled it since and it's made no difference.
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>> She mentioned today on refilling the car that range was under 400 miles and it's
>> normally just under 500. I think she thought (although she wouldn't say) it might be
>> down to me filling it with petrol at Tesco, the car is normally only fed
>> on Shell. However she's refilled it since and it's made no difference.
Thats a big difference. Thats not down to weather getting colder (the temperature has not suddenly plunged that much). I'd get the fault codes read.
Last edited by: Zero on Tue 6 Nov 12 at 22:56
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>> I'd get the fault codes read.
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It runs fine, so I doubt abything would show.
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>> First thing I would do is measure it brim to brim. Already said by others
>> above.
>>
The trouble is that that's never been done, so a figure produced now has no reference point.
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>>First thing I would do is measure it brim to brim.
To learn what pertaining to the opbservation that the consumption was lower a week or two ago??
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Italian Tune-Up time methinks.
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>> Italian Tune-Up time methinks.
>>
Done that. The MIVEC variable valve system doesn't cut in until about 3500 RPM and my daughter probably never gets to that engine speed.
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Hi BP
I have a Colt with that same engine, which I use for commuting. My trip computer has also been showing a reduction in economy for some journeys, mainly in the past week. I think it's a combination of factors including, having the engine running whilst scraping frost from windows, drawing more heat from the engine to keep the cabin warm and using the lights / heated rear window a lot more than in the summer.
Last edited by: Maisie's Dad on Wed 7 Nov 12 at 07:55
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>> My trip
>> computer has also been showing a reduction in economy for some journeys, mainly in the
>> past week.
Thanks - that's somewhat reassuring.
Can I also ask if yours mists up a lot? My daughter's car has optional a/c and it comes on automatically (but without any indication) when the air is directed to the front screen. It's one car where, due to its little engine, you really know the a/c is on! Daughter is aware of that (she's a pretty empathetic driver) so isn't driving any distance with it on.
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Mine is very predictable - once the temperature drops to less than about 8 on most of my journeys the trip computer quickly drops to about 58 rather than a steady 62-65 in the summer.
Once it gets below freezing, it drops to about 55 for the winter.
It was at 62 until about a week or two ago - morning/evening temperatures have been about 3 to 6 degrees, and it's now heading down, currently at 58.9. It's never reset, so will show some lag, obviously.
All observed since I've had the car.
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>> Can I also ask if yours mists up a lot? My daughter's car has optional
>> a/c and it comes on automatically (but without any indication) when the air is directed
>> to the front screen. It's one car where, due to its little engine, you really
>> know the a/c is on! Daughter is aware of that (she's a pretty empathetic driver)
>> so isn't driving any distance with it on.
>>
I'm not sure that my car has a misting problem as such. However, in colder or wetter weather, I do need to have some air flow directed to the windscreen to keep it clear (or I can put the a/c on).
I have to say, I've not noticed my a/c coming on when air is directed to the front screen! I don't find the car much more sluggish with the a/c on, but then most of my commute is on 30 / 40mph roads, with little need for brisk acceleration.
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>> Don't know if this helps:
>> www.car4play.com/forum/post/index.htm?t=8440&v=f
>>
Thanks for that - must admit I never think to look in that section on a day-to-day basis.
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Spent a bit of time with the car today. Wheels rotate freely so that's good. Nothing blocking the air intake (surprising small opening, tucked behind the leading edge of the bonnet).
So I took the car for a bit of a run with the MPG showing 42MPG and it seemed to stick there, although the route was mainly on rising ground. Figured out how to manually reset the computer, did that and drove a few miles home, mostly downhill, and arrived with the trip MPG showing 90MPG.
Switched the ignition off, and back on again, and the MPG showed 45. That was surprise, as I expected it to remember 90. So I'm minded to think that when it's on automatic (after the car has been parked for 4hrs) reset, then it may well be resetting to its overall average level rather than starting from zero each time.
Anyway, daughter will note the mileage on her next few fill-ups and we'll see what it's really doing.
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The winter blend petrol has lower calorific value.
I don't know why we still have it now 'nobody' has a carburettor.
(This post, and a few that followed were edited as Sooty asked for his email address to be removed from the subject header - Webmaster)
Last edited by: Webmaster on Mon 12 Nov 12 at 11:44
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I didn't think the UK had winter blend petrol. Are you sure that's right?
Last edited by: Webmaster on Mon 12 Nov 12 at 11:41
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>> I didn't think the UK had winter blend petrol. Are you sure that's right?
>>
There's definitely winter diesel but I've never seen a straight answer on petrol. Apparently the regulations (maybe law?) has summer, intermediate and winter petrol but I've no idea if that happens in practice.
It could be that there's a universal blend of petrol which is good enough to meet all 3 specs??
Last edited by: Webmaster on Mon 12 Nov 12 at 11:42
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I can find nothing to support Sooty TP's idea of winter blend petrol in the UK - perhaps he can provide some details.
Last edited by: Webmaster on Mon 12 Nov 12 at 11:42
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>> I can find nothing to support Sooty TP's idea of winter blend petrol in the
>> UK -
Section 5: www.legislation.gov.uk/uksi/1994/2295/contents/made
The dates are in there too somewhere, I think. IIRC it's a suprisingly early start and late finish.
Last edited by: Webmaster on Mon 12 Nov 12 at 11:42
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Interesting - That's something new I've learned today. Just ploughed through that lot and to summarise winter petrol is retailed from 1st September to 31st May and winter diesel from 22nd October to the 15th March.
Last edited by: Webmaster on Mon 12 Nov 12 at 11:42
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>> The winter blend petrol has lower calorific value.
>> I don't know why we still have it now 'nobody' has a carburettor.
>>
Lots of people still have carburettors.
Many of those are motorcyclists....
Last edited by: Webmaster on Mon 12 Nov 12 at 11:42
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Ah yes - the good old days (shudder) ! :-)
Last edited by: Webmaster on Mon 12 Nov 12 at 12:51
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Nothing wrong with carburettors that a good 3.5kg hammer will not cure.
Last edited by: Webmaster on Mon 12 Nov 12 at 11:42
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>> Nothing wrong with carburettors ECU's that a good 3.5kg hammer will not cure.
>>
That's fixed it for you......
Last edited by: Webmaster on Mon 12 Nov 12 at 11:43
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>> Nothing wrong with carburettors that a good 3.5kg hammer will not cure.
>>
Nothing wrong with carburettors full stop. Fine until some unsung berk decided to invent the autochoke.
What is important is knowing how to tune "your" carburettor.
My personal favourites were the SUs. Pretty much nothing to go wrong and will provide perfect service for decades in return for basic care and feeding.
From experience, people who hate carbs almost invariably used to either drive something sporting a fixed-jet carb, which suffered the inevitable jet clogging, or had the misfortune to experience the abomination that was the Ford VV series.
Last edited by: Webmaster on Mon 12 Nov 12 at 11:43
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>> From experience, people who hate carbs almost invariably used to either drive something sporting a
>> fixed-jet carb, which suffered the inevitable jet clogging, or had the misfortune to experience the
>> abomination that was the Ford VV series.
>>
>>
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Never had them. I grew up on twin choke Solexes (a fine instrument) and SUs of all shapes and sizes, single,twin and cold start one. And twin choke Webers.
All were great when you had tuned them. Until the next day when the barometric pressure changed significantly and then they needed to be retuned again.
EFI and ECUs are the best invention for DIYers since the disk brake..
(Apart form those designed by the French..or installed by Italians of course :-)
Last edited by: Webmaster on Mon 12 Nov 12 at 11:42
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Re: (This post, and a few that followed were edited as Sooty asked for his email address to be removed from the subject header - Webmaster)
Missed the post @ Sun 11 Nov 12 12:04
Last edited by: John H on Mon 12 Nov 12 at 12:26
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>> Missed the post @ Sun 11 Nov 12 12:04
Ta. Edited that as well now
ps, you have email.
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>>>Lots of people still have carburettors.
>>>Many of those are motorcyclists....
They shouldn't be out in ice.
So not starting would be a blessing in disguise.
I'm not linked to the petroleum industry anymore, but when I was, I learned that they used to dissolve LPG into the petrol in a pressure pipe with a choke each end so the pressure could be high in that section, and LPG as liquid was suffused which would not turn to gas, but would dissolve or disperse into the fuel and change it's vapour phase characteristics.
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Mitsubishi Colt 5-door - MPG gone right off - cold weather? - R.P.
