MK7 GTD - Real Life MPG

[jivemonkey]

For the last 3 days I've been doing another little test with my normal trip to work and getting on average around 45mpg, the only change I did was set the climatronic 'auxiliary heater' to disabled in the setup menu. 

I can honestly say I didn't notice too much of a difference with the time it took to heat the cabin, and the heated seats really help it feel more warm than it is anyway. To see whether there would be any significant difference I thought i'd enable it again this morning. Got to work and MPG down to 41.

I didn't go as far as checking ambient temperatures each day but it's been fairly consistent around 5 degrees the last few days. Can only attribute the loss of MPG to the heater...anyone else tried this? I believe it draws around 80A when active and doesn't turn off until the oil temp reaches 70 degrees.

[stuart.cameron]

Hmmm. Will have to try this!

[corgi]

For the last 3 days I've been doing another little test with my normal trip to work and getting on average around 45mpg, the only change I did was set the climatronic 'auxiliary heater' to disabled in the setup menu. 

I can honestly say I didn't notice too much of a difference with the time it took to heat the cabin, and the heated seats really help it feel more warm than it is anyway. To see whether there would be any significant difference I thought i'd enable it again this morning. Got to work and MPG down to 41.

I didn't go as far as checking ambient temperatures each day but it's been fairly consistent around 5 degrees the last few days. Can only attribute the loss of MPG to the heater...anyone else tried this? I believe it draws around 80A when active and doesn't turn off until the oil temp reaches 70 degrees.

So 80A on a 12v system is about 960watts - the total output of the engine is 135kW... of which in normal driving you might use on average say 40kW. 960w is 2.4% of the average power you use... Even assuming that the auxiliary heater is on all the time (i.e. your journey is short enough for engine temp not to reach 70C) then you should expect to see no more than 1mpg difference.

That's a fairly rough and ready calculation but I suspect the cause of the change lies somewhere else... passive regen, possibly

[stuart.cameron]

Made no difference on the way home! But it was with a different tank of fuel.

Anyone compared jet to shell?

[KyleB]

Out of interest (probably me being completely stupid) how do you disable the heater?

[monkeyhanger]

Not used Jet yet, but i'm almost at the end of my Shell fuelsave tank and it looks like it's going to be around 43mpg actual. The response of the car seems a little laggier than normal when you first put your foot down from lowish revs but after that initial lag the car responds very well. The car's mpg has been generally ok, except when the regens have happened. On Shell, the regens have hammered my mpg, giving me around 36mpg for the regen affected commute, when Esso or BP would have dipped to around 40mpg.

For my experiences I would have to recommend BP standard diesel highest for overall mpg and response/performance, followed by BP, Sainsburys, Shell fuelsave and Shell V-power. Apart from the V-power (41mpg), there hasn't been a massive difference in overall tank mpg between them (43 - 45mpg), and I have yet to do a really long journey (>100 miles) in my GTD.

Anyone else have a "favourite" fuel?

[monkeyhanger]

For the last 3 days I've been doing another little test with my normal trip to work and getting on average around 45mpg, the only change I did was set the climatronic 'auxiliary heater' to disabled in the setup menu. 

I can honestly say I didn't notice too much of a difference with the time it took to heat the cabin, and the heated seats really help it feel more warm than it is anyway. To see whether there would be any significant difference I thought i'd enable it again this morning. Got to work and MPG down to 41.

I didn't go as far as checking ambient temperatures each day but it's been fairly consistent around 5 degrees the last few days. Can only attribute the loss of MPG to the heater...anyone else tried this? I believe it draws around 80A when active and doesn't turn off until the oil temp reaches 70 degrees.

So 80A on a 12v system is about 960watts - the total output of the engine is 135kW... of which in normal driving you might use on average say 40kW. 960w is 2.4% of the average power you use... Even assuming that the auxiliary heater is on all the time (i.e. your journey is short enough for engine temp not to reach 70C) then you should expect to see no more than 1mpg difference.

That's a fairly rough and ready calculation but I suspect the cause of the change lies somewhere else... passive regen, possibly

Something else to remember is that unless you've got temp and fan speed maxed out, you're unlikely to be drawing anywhere close to the 960W. I mainly have my cabin temp set to "LO" when it is above freezing, so i'm rarely drawing on the auxillary heater. I wonder what the current draw of the heated seats system is when you've set them to "toasty".

Maybe when the car is up to temp, not using the heaters actually has a negative effect on mpg, because the cooling system is working hard to shed excess heat rather than using it to heat the cabin ventilation air.

[KyleB]

Anyone else have a "favourite" fuel?

As I've said before, for me, best results have been from Asdas finest*

*read cheapest.

[Gordor]

It has been mentioned on here before but early into your journey, you can make the stop start operate when at standstill by turning the heat temperature down. I'm on Sainsbury's, with MH's settings (also mentioned before) operationally, flooring it properly when I can but then changing at 2000 revs when driving normally (which is a lot at the moment as I work in Somerset if you have seen the news) last few days plus 50mpg, best ever. Mileage is 9500

[monkeytennis]

Up to 3.8k now, filling up with nothing but BP Ultimate, from a mix of motorway and rural roads/traffic last tank managed 42 mpg