Diesel Consumption in Winter
11-24-2006, 03:47 AM
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Fitting the replacement for my blown turbo coincided with the onset of chilly weather here in the UK. My average fuel consumption has dropped from 40'ish to 36'ish. This is my first diesel car and I know they take a little while longer to warm up. I also don't go on very long runs (10-30 miles average). My E39 520i petrol predecessor would drop 1-2mpg in winter.
Coincidence and just normal for a diesel ?
Coincidence and just normal for a diesel ?
11-24-2006, 05:29 AM
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Originally Posted by Ian' post='360030' date='Nov 24 2006, 12:47 PM
Fitting the replacement for my blown turbo coincided with the onset of chilly weather here in the UK. My average fuel consumption has dropped from 40'ish to 36'ish. This is my first diesel car and I know they take a little while longer to warm up. I also don't go on very long runs (10-30 miles average). My E39 520i petrol predecessor would drop 1-2mpg in winter.
Coincidence and just normal for a diesel ?
Coincidence and just normal for a diesel ?
ABC
11-24-2006, 05:54 AM
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Originally Posted by aybeesea' post='360054' date='Nov 24 2006, 02:29 PM
Did the IDrive get reset to US gallons during the turbo replacement. It IS the default...
ABC
ABC
cheers
steve
11-24-2006, 06:02 AM
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Originally Posted by steve_gus' post='360063' date='Nov 24 2006, 02:54 PM
not a beemer, but the renault diesel im exchanging in a week or so does approx 42-43 when its cold, when it would normally do 45-47 otherwise. This is on a 50 mile run to work at an average speed of 45 mph (80 and 50 mix mostly)
Is there some engineering or thermodynamic principle being indicated here?
ABC
11-24-2006, 08:00 AM
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My 530D gives 31.6 in summer 29.7 in winter.
Reasons,
1, Diesel engines take much longer to warm up than petrol.
2. More electrical gadgets switched on = more power drain.
3. Wet roads increase rolling resistance of tyres considerably
4. And...I think.....Colder fuel means the 'calorific value' is reduced, for a given amount of fuel by volume you get less energy out. So you have to use more for the same power. (I'm sure Znod or one of the other technical experts will put me right here!)
The biggest effect is with number 1. the others contribute in smaller ways but together account for higher consumption for all cars in winter.
Reasons,
1, Diesel engines take much longer to warm up than petrol.
2. More electrical gadgets switched on = more power drain.
3. Wet roads increase rolling resistance of tyres considerably
4. And...I think.....Colder fuel means the 'calorific value' is reduced, for a given amount of fuel by volume you get less energy out. So you have to use more for the same power. (I'm sure Znod or one of the other technical experts will put me right here!)
The biggest effect is with number 1. the others contribute in smaller ways but together account for higher consumption for all cars in winter.
11-24-2006, 08:02 AM
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Originally Posted by Ian' post='360030' date='Nov 24 2006, 02:47 PM
Coincidence and just normal for a diesel ?
The cold starts is the key.
I cold engine has to do so much more work with all the stiff oils etc.
11-24-2006, 08:06 AM
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Originally Posted by Ricracing' post='360128' date='Nov 24 2006, 06:02 PM
All cars and enginetypes consumes more fuel when it's cold.
The cold starts is the key.
I cold engine has to do so much more work with all the stiff oils etc.
The cold starts is the key.
I cold engine has to do so much more work with all the stiff oils etc.
11-24-2006, 08:17 AM
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I got 41.5 mpg from my 530d today over 230 mainly motorway miles, even including M1 Northbound traffic jams 
11-24-2006, 11:42 AM
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Originally Posted by KAF' post='360126' date='Nov 24 2006, 05:00 PM
My 530D gives 31.6 in summer 29.7 in winter.
Reasons,
1, Diesel engines take much longer to warm up than petrol.
2. More electrical gadgets switched on = more power drain.
3. Wet roads increase rolling resistance of tyres considerably
4. And...I think.....Colder fuel means the 'calorific value' is reduced, for a given amount of fuel by volume you get less energy out. So you have to use more for the same power. (I'm sure Znod or one of the other technical experts will put me right here!)
The biggest effect is with number 1. the others contribute in smaller ways but together account for higher consumption for all cars in winter.
Reasons,
1, Diesel engines take much longer to warm up than petrol.
2. More electrical gadgets switched on = more power drain.
3. Wet roads increase rolling resistance of tyres considerably
4. And...I think.....Colder fuel means the 'calorific value' is reduced, for a given amount of fuel by volume you get less energy out. So you have to use more for the same power. (I'm sure Znod or one of the other technical experts will put me right here!)
The biggest effect is with number 1. the others contribute in smaller ways but together account for higher consumption for all cars in winter.
11-24-2006, 11:59 AM
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the more power with cold air' is always an interesting one. Although its true, does anyone ever drive thier car on a cold day and think hey, this is faster today - dont think so - the effect must be pretty marginal.
the example I gave on my car was for a full 50 mile journey, each way, each day, over 2 years, so im pretty sure its not just the first few miles of warm up.... not over a 50 mile journey.
If the air charge is more dense, then there needs to be a proportionately bigger amount of fuel added ..... this makes sense no?
On the other hand, it might just be crappy engine mapping, overfuelling a bit to help with what would otherwise be a lumpy engine response.
In less than a week i will abe able to see how a 520d compares, as least in the cold
cheers
steve
the example I gave on my car was for a full 50 mile journey, each way, each day, over 2 years, so im pretty sure its not just the first few miles of warm up.... not over a 50 mile journey.
If the air charge is more dense, then there needs to be a proportionately bigger amount of fuel added ..... this makes sense no?
On the other hand, it might just be crappy engine mapping, overfuelling a bit to help with what would otherwise be a lumpy engine response.
In less than a week i will abe able to see how a 520d compares, as least in the cold
cheers
steve