Having a discussion on another forum and it has been proposed that because of the additives they put in diesel to stop it freezing during the winter months that it drops the MPG down.

I am not 100% convinced and think that the additives are in there all year round but maybe someone can verify this ?

I also think that you should get a better mpg return because the air entering the engine is cooler and thus more dense which in turn means you get more power and have to use less throttle, anyone have any ideas on this ?

:confused:

Will the car run richer when the engine is cold too (which will be for longer in this weather?). I've not noticed a marked difference in fuel economy on my diesel over the last few months, but I did notice quite a difference in the Fabia, although that may also have been cos it was due approaching a service?

Chris

All cars are less economical the longer they take to warm up. That should be obvious. Colder temperatures = choke open for longer = more fuel being burned.

I also think that you should get a better mpg return because the air entering the engine is cooler and thus more dense which in turn means you get more power and have to use less throttle' date=' anyone have any ideas on this ?

:confused:[/quote']

My thoughts on this are that if the air is more dense then to maintain an equal air/fuel ratio, more fuel will also be needed lest the engine run lean. Ok so you may lose a few mpg (I'm certainly noticing the difference over winter) but you gain a few bhp/lbfts as compensation.

I also agree with ScoobyChris's posts regarding longer warm up times.

Would having lights on, heated rear window and heater fan on more affect it? I'm sure driving the same at night with xenons on gives 1-2 mpg less than the same kind of drive during the day. Purely based on the evidence from the trip computer...

Would having lights on, heated rear window and heater fan on more affect it? I'm sure driving the same at night with xenons on gives 1-2 mpg less than the same kind of drive during the day. Purely based on the evidence from the trip computer...

It should definitely have an affect. On the flip side though, in the warmer months you might switch the air con which would cause a similar drain?

Chris

This is normal. Every car I have owned has worse mpg in winter!

As all have said, all the extra electrics can sap 10% and winter fuel around 5% less mpg. At this time of year you can run cheaper supermarket fuel as the majors don't put in the performance additives as they affect the winter anti waxing agents.

At this time of year you can run cheaper supermarket fuel as the majors don't put in the performance additives as they affect the winter anti waxing agents.

Is this fact or rumoured??

Fact, i work for a major.

Electrical load has less of an effect than on a petrol wher they can loss upto 20%. All down to the altenator load.

Between winter electrical loads, fuel and new tyres I'm down over 20% in fuel consumption.

Weird, maybe the cold weather makes me drive safer due to less traction but my work commute is up to 53mpg average where it's normally 50ish :confused:

I considered posting a 'Does cold mean better mpg' thread - the Stevie Science being cooler air = more power therefore more efficient at a given engine speed. Never considered that the car would introduce more fuel to accomplish this.

Having a discussion on another forum and it has been proposed that because of the additives they put in diesel to stop it freezing during the winter months that it drops the MPG down.

I am not 100% convinced and think that the additives are in there all year round but maybe someone can verify this ?

I also think that you should get a better mpg return because the air entering the engine is cooler and thus more dense which in turn means you get more power and have to use less throttle' date=' anyone have any ideas on this ?

:confused:[/quote']Somewhere in the Skoda handbook I think it states the dates on which diesel changes grade from 'summer' to 'winter', so yes the fuel does change with the seasons and yes the winter grade does give worse mpg (only 2-3 mpg though).

My best mpg figures have all been in summer; dry bright conditions, good fuel, low winds, low electrical load etc seem to more than cancel out the warmer intake air.

All cars are less economical the longer they take to warm up. That should be obvious. Colder temperatures = choke open for longer = more fuel being burned.

Why should it be obvious ?

If you want to make more power on a turbo car one thing you can do is fit a larger intercooler on, isn't this effectivly like driving on a colder day ?

This produces more power or a larger bang in effect.

Can you can't really run a diesel lean.

so you can't really run a diesel lean.

On the contrary, you're nearly always running a diesel lean!

Rob.

On the contrary' date=' you're nearly always running a diesel lean!

Rob.[/quote']

Cheers Rob

So this brings me back to my first point, colder air more power, less diesel used ?

So this brings me back to my first point, colder air more power, less diesel used ?

As far as I'm aware (not a mechanic!), diesels don't have a "choke" or the modern equivalent. Therefore, a cold diesel engine isn't going to use more fuel than a warm diesel engine, and an increase in the density of the air isn't going to result in an increase in the amount of fuel required.

I'd say it's down to the fuel grade (ie. what bryand said).

Rob.

Thought so Rob. The more diesel used the more soot produced anyway which means the engine isn't burning the fuel properly in the first place which mean less power is achived if the mixture isn't right.

I'm definately getting less mpg according to the trip. I've got a regular 10 mile trip through the Gatso'd up roadworks on the M60 and some A roads on each end. I was getting 55-57mpg at the end of the summer, I'm struggling to beat 53mpg at the moment.

I've noticed that Shell Diesel Extra has been quite rare around 'ere lately, dunno if this is anything to do with temperature?

As far as I'm aware (not a mechanic!)' date=' diesels don't have a "choke" or the modern equivalent. Therefore, a cold diesel engine isn't going to use more fuel than a warm diesel engine, and an increase in the density of the air isn't going to result in an increase in the amount of fuel required.

I'd say it's down to the fuel grade (ie. what bryand said).

Rob.[/quote']

Hi Rob

Possibly the diesel will need extra throttle to produce the same power when cold as more of the energy from the burnt fuel is being drained into the engine block while it is warming up and hence nt driving thecar forward. Probably not as noticable as petrol cars where rich mixture is needed to sustain the combustion.

Chris