[Tourer_Guy]

Hi Everyone,

As many of you no doubt know, the cloud point of diesel is the temperature at which wax within the fuel solidifies and you start getting solid wax clogging up the filters and fuel line.  Major fuel manufacturers therefore alter the blend from summer to winter (and between regions) to ensure general users aren't affected. 

I've noticed, though, that my winter fuel consumption is slightly higher than when the weather was warmer, despite my driving and regular routes remaining the same.  I've gone from an average of 4.9l/100km to 5.1l/100km.  Now this could well be explained by the fact that it gets quite cold where I live (regularly gets down to minus 5 degrees C) and the engine takes longer to warm to operating temperature.  It would seem logical that more fuel would be injected while the engine is cold to ensure smooth running and longevity, and this would lead to an increase.

Does anyone think the blend of fuel would also be a factor?  Has anyone here noted different fuel consumption while using winter or alpine diesel (although driving in mountains is different to driving on fairly flat freeway)?

Anyone have any thoughts about this?

In other news, my i30 is still going strong 5 months in.  I still love it, especially the practicality of the wagon and it's ability to swallow large amounts of cargo.

Cheers,
Tourer Guy.

[The Gonz]

I don't have the knowledge but I do have Firty's consumption as observation. During the current cold spell (I'm wearing a hoodie indoors ) she's running at 4.5 instead of her usual 4.1, while she still gets 3.8 cruising on straights once she's warm, so I can see the cold definitely affecting cold starting performance.

[Tourer_Guy]

3.8-4.1 are seriously good numbers - well done!

I have seen 3.7 once on a short, flat trip sitting on 90km/h, but couldn't keep it that low.  I'd love to do a longer trip to see how it would go.  My best so far has been 4.4 on a two hour freeway run.

Thanks for the quick response, I am fairly sure the cold starts and slow warm up are contributing more to the change in consumption than the blend of diesel.

[The Gonz]

I'd agree. I wasn't aware of any change in diesel composition across the year (exculsively using BP Ultimate since purchase - dealer recommendation) but the current economy dive (car, not country) has had me thinking of trying Caltex or Shell. One of the members suggested one of the alternatives gets the engine to run more smoothly.

[Phil №❶]

Diesel is a bit like a cake actually, in that it consists of a variety of ingredients. Change any of them and you still have Diesel, but not the same Diesel. I have no knowledge of actual differences between the standard recipe and winter recipe, but if the calorific energy is altered, then so too, will consumption be altered. The diesel being a thermo engine will use slightly more fuel in winter to achieve & maintain it's correct operating temperature. With air @ -5 @ 100 kmh, that represents quite a cooling force, which has to be compensated for by burning fuel.

To further complicate things, cold moist air is good for combustion engines, so efficiency can increase under these conditions, but @ freezing temps, the air is dry, so there can be less power produced as there is no water vapor to expand in the combustion chamber.

[The Gonz]

Ah yes, I do recall seeing aftermarket water injection systems back in the crazy 80s when I drove carburettors.

[PhireSideZA]

I have seen 3.7 once on a short, flat trip sitting on 90km/h, but couldn't keep it that low.

I had a 140kg 550cc motorcycle that could only dream of these figures!! Figures like this from a 4 cyl diesel weighing way over a ton is excellent! Well done

[Tourer_Guy]

I have seen 3.7 once on a short, flat trip sitting on 90km/h, but couldn't keep it that low.

I had a 140kg 550cc motorcycle that could only dream of these figures!! Figures like this from a 4 cyl diesel weighing way over a ton is excellent! Well done

Cheers!  That was a short run (about 10km) on dead flat freeway sitting on 90km/h, so probably about as good as it's possible to get without hypermiling.  I'm keen to take it for a longer freeway run to see how it goes.  If it can average 4.5l/100km over a longer trip sitting on the speed limit I'd be extremely happy.

[Lakes]

Hi Tourer_Guy, that's an interesting observation. i knew they do that with the fuel in alpine region's.
It bring's back memories of an original i30 owner's member called Thumper, he also came from your region. he noted his economy went down as temp's went down. so he made up a cover for the intercooler ( turned out to be cardboard cut out ) he used to put that in front of the intercooler & claimed his economy improved. at the time i liked in Sydney & tried that trick, but i can't say i noticed anything. like winter economy drops very slightly. i put it down more to the ECU changing the tune to compensate for air quality. but was never that noticeable on trip just on short drives in winter. you could try covering the intercooler but i latter disregarded that never used it again. Thumper had some wild idea's to reduce his fuel bill  maybe if you do a search back to 2008 you will find some of his posts?
enjoy your new car. i went from 4.7L 5.2L/100k to 8.5L/100k sometimes 9L/100k & enjoying it 
cheers

[Asterix]

My i30 allways use more fuel in the winter, normally around 0,25 L/100 extra.

It takes a lot more fuel to warm up the engine and more power is used for the heated seats, heated rear window, a/c and high speed on the cabin heater to defog. All this produces more load on the generator.

Winter temperatures here are normally between +5 to -10 but we do get down to -20 now and then... 

[sundiz]

The fuel consumption usually rises in cold weather. That is mainly because it takes a lot more time for the engine to heat up to is normal operating temperature. For that reason motor heaters (electrical or fuel based) are recommended to be used before starting the car when temps get under +5'C. Cold temp might affect a little bit to the fuel consumption, but the main cause are cold starts. Here the temperature can easily variate 60*C during a year (-30 to +30*C) and the worst fuel consumption can be achieved by driving short distances during cold periods.

Of course the cold temps require winter diesel.. But like it has been said: diesels are like cakes. There are many different recepies. Looked from local fuel suppliers web page that they have 7 different diesels here in Finland. The most "warm" diesel has minimum temps of 0- -10*C and the most "cold" diesel has minimum temps of -40- -44*C. In some older 80's cars you can add petrol to the diesel to make it more running in cold temps. If i remember right you were allowed put up to 20% petrol in to the diesel in old mercs. But that trick won't work with modern diesel engines...

Some have said that the winter diesels are a bit "dry" when compared to summer ones. Like the winter ones do not lubricate the pump as well as the summer ones. In old days people added 2-stroke oil to the diesel in winter time to lubricate the fuel pump more better. But I guess the modern diesel fuels have been desingned so that you don't need to add any oils or petrols to the diesel. Or at least the modern engines can't handle those kind of self mixed "hybrid" fuels.