1st fill up and MPG is bang on

[Richf]

Assume he's referring to anti-waxing additives added to most diesel fuels upon delivery to the filling station - may add less, or none, over summer months?

I assumed something along those lines , love to know where this idea came from

[dippo]

http://en.wikipedia.org/wiki/Winter_diesel_fuel

[Richf]

Not applicable in the UK of course

[ksr]

Not applicable in the UK of course

Why so, Rich?

That wiki says:

United Kingdom

The United Kingdom differentiates diesel fuel into Summer and Winter Fuel according to BS EN 950^[31] and BS EN14214 (biodiesel).^[32][33] The same numbers are used in the Republic of Ireland. Distribution of winter biodiesel in the United Kingdom starts in November and ends in March.^[31] Designation CFPP value time frame Cloud Point Summer Fuel -5 °C 16.03. - 15.11. 3 °C Winter Fuel -15 °C 16.11. - 15.03. -5 °C

[Richf]

Winter fuel is not the reason diesels use more fuel during the cold weather , barking up the wrong tree there

[JakeBlade]

Winter diesel has a lower CV because of the volume of additives included, so you end up getting less energy per litre from the fuel than summer fuel. Less energy per litre in the fuel will result in less mpg.

[RussD]

I suspect the reason we get lower winter mpg is the engine is colder, takes longer to warm up (because its colder) and also have heated windows, blowers, seats etc all going causing more drain on the electrical system to restore.... my Greenline II is around 1.5 mpg optimistic (in fact, every VAG group car I've had from 3 Passats (1.9l 110, 1.9l 130, 2.0l 140) and A6 (2.0l 136) have been around the same amount optimistic) - you can't use a single tank as a measure anyway (regardless of how many clicks you let the pump to before stopping) as the margin of error will still be too large to be accurate - average over 20, 30, 40 fill-ups and you'll get a better idea of how much its really out. I've filled-up 41 times over 21,000 miles and the trip averages 1.3 mpg "over" ("best" 0.2 mpg, "worst" 2.7 mpg) ... I'm seeing a jump from a true (calculated, not trip computer) 59.9 in the winter to a true 65.3 now it's warmer.... was pleased with 59.9!

[Richf]

^

Is the right answer

Petrols also use more fuel during the winter for the same reason the additives have no appreciable impact , not here in the UK at least

[dippo]

My car was in for service today, so I mentioned the fact that my fuel consumption display was reading 15% higher than the actual according to fuelly. They came up with a solution which I'm sure will be good news to Skoda owners everywhere: they told me to ignore it!