Diesel fuel consumption in winter.

[johnnyb44]

Hi.
Call me a saddo if you want ( you'll be right in doing so ) but I've always kept meticulous records of what my car does to the gallon on a brim to brim bases.
In doing so i think it gives a good indicator of the general health of your engine. There are many factors that can affect your mpg like dirty injectors ,poor fuel, blocked filters and even down to sticking brakes and low tyre pressure so thats why I've always kept records ( plus im a sad old *** )
One thing I've noticed is that my car definitely returns more to the gallon with the maf disconnected based on overall figures Poorly maf no doubt. When the outside temp reaches the low to mid 20 s the mpg starts to drop off to around 40 to the gallon.If the outside temp hovers between 13 to 21 degrees my car will return around 42 to 45 but this is the exception ( 45 ) .
Now that the cooler weather has arrived its dropped to 40 mpg and know matter what driving style i adopt it doesn't change significantly. Also I've noticed. different fuel fuel has a surprising affect on the economy of our cars. Morrisons diesel has a dire affect on my car with it dropping to below the 40s while shell nitro diesel is very good. But not all cheap fuel has had a negative impact on my car There's a garage in Welshpool selling diesel as we speak for 1.25 a litre. It one of these that sells the unbranded stuff with a convenience store bolted on to it. I've been getting some 45mpgs out of this stuff ..
So do our diesel cars mpg generally decrease with the onset of winter or should it stay around the same all year round. Do fuel company's change there diesel mixture / makeup during the winter months to aid cold starting and would this affect its efficiency.
I forgot to mention that my diesel is an auto and over the last year its total average mpg over 16 k is 42 ,3 mpg. This time over the year its now doing a weekly average of 40,7 mpg.
My driving is virtually ground hog day with no congestion so week in week out its hardly varies.
If your still awake after reading this thanks for looking
Johnny

[T-Cut]

Lots of statistics, but no mention of the running temperature. Logically, the cool running diesel engine runs even cooler in winter and that will have an impact on fuel consumption. What temperature does it typically run at?

TC

[Jim W]

Don't forget when temps drop to 5 or below your fuel burning heater will kick in if you have one fitted meaning your mpg will go down again think its about a litre an hour your fbh uses

[johnnyb44]

The car runs at around 86 to 87 degrees and thankfully this year I've managed to get the fbh up and running after loads of help from here.

[DMGRS]

In winter it'll use more fuel - longer warmup times and more use of electrical devices such as headlights and heater blowers. I've noticed around 3MPG difference as an average between winter and summer, my diesel cars always seem to suffer with the issue more than petrol engined versions.

[johnnyb44]

Hi Mat.
That didn't even enter my head to be perfectly honest. You just take headlights , rear window heaters for granted without thinking about the impact on fuel consumption. Since the clocks were changed i now travel to and back from work with the lights on. That's 200 miles a week with the extra load on the engine. I suppose it all mounts up over a week.