Since I came home on Sunday the trip computer on my TDv8 has been showing mpg's varying between 30.0mpg and 36.5 (that's the best I have ever seen and it was averaged over 16 miles on a flat road at 60mph). Normally I only see over 30mpg after driving all day at 70 on the cruise, not in A road driving with speed variations and other traffic when I see between 26 and 28mpg depending on how I drive the car.

Now I can put this down to only 2 things:
a) It has been pretty cold around here - day time temperatures not above +5C
b) My Trip Computer is having a seizure

Theory a) If the ambient air temperature is low then the intercoolers are not having to do so much air cooling for the charge air or they can cool much larger quantities of air so I am burning more air in the mixture than normal thus making the engine more efficient.

Any automotive engineers care to give an explanation of why my fuel economy is so much better in cold frosty weather than warm days? Bear in mind that as a result of the cold weather I am using things like the seat heaters, screen heaters, interior heater and FBH much more than normal and these all put a big load on the engine and should increase fuel consumption rather than reduce it. 2020 Pangea Green 1st Edition D240 New Defender 110 is here and loving it
2018 Melting Silver Mini Countryman PHEV - soon to be replaced
2015MY Corris Grey SDv6 HSE Dynamic, the best car I have ever owned, totally reliable only a cou0le of rattles in 3 years, now no longer in my care
Also in my garage is a 1996 TDi300 Defender 90 County HT made into a fake CSW

Does this help Tim?

http://www.articlesbase.com/cars-articles/...41281.html 

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The article is opposing Tims findings then...

Looks like it... several Google results seem to all point to the same fact  

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Maybe the cold, more viscous fuel taking longer to get to the engine is fooling the trip computer that it is burning less  2020 Pangea Green 1st Edition D240 New Defender 110 is here and loving it
2018 Melting Silver Mini Countryman PHEV - soon to be replaced
2015MY Corris Grey SDv6 HSE Dynamic, the best car I have ever owned, totally reliable only a cou0le of rattles in 3 years, now no longer in my care
Also in my garage is a 1996 TDi300 Defender 90 County HT made into a fake CSW

Or you are drinking something to warm yourself up early in the morning and are not reading the carputer correctly....  Range Rover Vogue ‘17 TDV6

Gone: Range Rover Vogue '11 4.4TDV8, Range Rover Sport ‘59, Range Rover Sport ‘56

Or.............................. the oil majors add dewaxing agents to diesel in the winter and my car rather likes it! 2020 Pangea Green 1st Edition D240 New Defender 110 is here and loving it
2018 Melting Silver Mini Countryman PHEV - soon to be replaced
2015MY Corris Grey SDv6 HSE Dynamic, the best car I have ever owned, totally reliable only a cou0le of rattles in 3 years, now no longer in my care
Also in my garage is a 1996 TDi300 Defender 90 County HT made into a fake CSW

Or you're not using the air con.
I noticed that using only the heater (ECO) reduces my consumption by 1/1,3 l/100km

I saw the same thing happening as Tim, and then realised that I had not added my usual 400ml 2-stroke oil into the diesel, last time I filled 'er up.

Duh!

KB RRS TDV8, black with ivory.

Never believe your trip computer

KB, do not mind me asking by why the hell do you put 400ml 2-stroke oil into the diesel?

Coko,

It has all been discussed before; http://www.rrsport.co.uk/forum/topic10453.html?highlight=2stroke

In essence, by adding high quality (JASO C or D), semi-synthetic, 2-stroke oil, in a 1/200mix, to your diesel, you get a better burn, especially in cold climates. It mixes with the diesel, lubricates the engine, and has a better burn, resulting in 5-7% better driving economy, easier cold-starts, less smoke, and a more quieter motor.

I have used this since I got the TDV8, and even long before, in my diesel Volvo Penta Z-drive boat engine.

KB RRS TDV8, black with ivory.

I remember a tuner explaining that Turbo Chargers operate much more efficently in colder weather. When I had the RS4 on the rolling road they chilled the air in front of the car as the workshop was very warm, to get a realistic dyno graph. Not sure if more efficent turbo chargers equates to better fuel consumption or not

Red1903 wrote:

I remember a tuner explaining that Turbo Chargers operate much more efficently in colder weather. When I had the RS4 on the rolling road they chilled the air in front of the car as the workshop was very warm, to get a realistic dyno graph. Not sure if more efficent turbo chargers equates to better fuel consumption or not

Ambient air is more condenced the colder you get, most Diesel and Petrol engines will run better in these conditions as more air is forced into the chambers making the Engine more efficient, thats why most engines appear to have better performance in damp or wet conditions (natural air cooling and condensation)