Winter fuel consuption

depronman

A2OC Donor
I was getting a regular 62 to 65mph in the Summer / Autumn weather. This consisted of my daily commute to work which is 8 miles each way on mainly 30mph roads and a fair few sets of traffic light and road junctions the odd motorway run at 70/75mph, normally either just me in the car or one other. I was very pleased with this, especially considering the millage on the A2

I went on holiday about month ago for 2 weeks on on my return to the UK Winter had arrived, very cold over the last few weeks. I filled up today and only got 55mpg, I was expecting it to be lower as the webasto has been in use a lot and the heater was only blowing hot about half way home from work plus the temp gauge never hit 90deg on my work commute. I did try turning the webasto off (Econ mode), but the temp gauge never moved on the 8 mile work commute and the heater was only look warm at the end of the journey.
I changed the thermostat in the summer and with more normal outside temperature I got to 90deg after about 3 to 4 miles

I'm not overly concerned, as 55mpg is not to be sniffed at, really just wondering if this is typical winter drop of on MPG on the TDI or have I something going wrong

Anyone feedback would be welcomed

Cheers,
 

AndyP

Member
I am amazed you were getting such good mileage on short journeys, I notice the difference if I swap from my 35 mile to 25 mile (each way) commute.
However,apart from that, yes mine has also going down from 61/62 to about 55/56. At the moment I'm blaming it on my new wider, heavier wheels and tyres, so I have temporarily swapped back to my 15" wheels to prove it.
 

depronman

A2OC Donor
I am amazed you were getting such good mileage on short journeys, I notice the difference if I swap from my 35 mile to 25 mile (each way) commute.
However,apart from that, yes mine has also going down from 61/62 to about 55/56. At the moment I'm blaming it on my new wider, heavier wheels and tyres, so I have temporarily swapped back to my 15" wheels to prove it.
Maybe you need one of my remap's :) I'm convinced it is better on fuel since the remap, not a great amount but better
I will see what it does on the next tank full, hopefully the weather will play nice and temperature wise stay where is at the moment (10 deg C)
 

AndyP

Member
Maybe you need one of my remap's :) I'm convinced it is better on fuel since the remap, not a great amount but better
I will see what it does on the next tank full, hopefully the weather will play nice and temperature wise stay where is at the moment (10 deg C)
I'm sure I do, and if you could apply your changes to my later map I would be eternally grateful etc. However, I may also need a new temperature sensor ... I have already replaced the thermostat because it seemed to take forever to warm up, that that made no difference ...
 

depronman

A2OC Donor
If the temp sender is telling the ecu as well as the gauge that it is cold then this will hammer you mpg the furling map that is used at 0 deg C inject more than twice as much fuel pee stroke as the furling map used at 90 deg. There are a fair few furling maps between 0 deg and 90 deg each progressively injecting less fuel


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Alan_uk

A2OC Donor
There have been some long threads in the past on mpg. I recall from memory one comment that in winter headlights etc can knock 3mpg off the fuel consumption.
 

depronman

A2OC Donor
There have been some long threads in the past on mpg. I recall from memory one comment that in winter headlights etc can knock 3mpg off the fuel consumption.
Yes I can see that, headlight on, flower motor on 3 or 4, heated rear window on, and alternator recharging the battery after a coldstart - it all adds up to a fair bit of extra load and it as to come from somewhere.

I think the biggest culprit for the drop in MPG that I saw over the cold snap was the webasto aux heater and the ECU fuelling the engine with more fuel due to colder ambient temperature. The Webasto was on a lot in town driving, with it switched to ECO (off) the temp dropped from 90deg as I hit town to 60deg after 10 mins to get through town, I then got on the motorway and after a couple of miles at 70mph the temp gauge was back at 90deg with webasto still off. It would appear than when ambient temp is around 0 to 3 deg and the heater is on hot/blower on 3 or 4 then the heater is consuming far more heat than the engine is providing, hence the webasto kicks in to make up the difference and this is what hurts the fuel consumption.
 
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