What the difference? GTD Blueline..

[GTDING]

The CO2 is the same figure for both Blueline and standard at 125g/km...

[fredgroves]

BTW I asked VW themselves about the difference and the difference IS only the 17's vs the 18's. Nothing else.

[phope]

In the current brochure, it states that the Blueline version are 6g (manual) and 7g (DGS) of CO2 less than the normal GTD versions respectively

[fredgroves]

Yes, sorry, when I said the difference was only the wheels, its only the wheels which make the difference in CO2 emissions.

[corgi]

How much weight would they be saving over an 18inch?

It could be significant depending on the wheel and tyre used. Also, the rim is, in reality, the heaviest part of the wheel when in motion and that mass is further from the centre of the wheel and therefore requires more power to accelerate at the same rate. This assumes that the wheels/tyres are the same width, of course...

There will be a number of elements that affect performance relating to the wheels but although the wheels are smaller the overall rolling circumference of 17/18/19 inch wheels will be the same (or as near as makes no difference) owing to the profile of the tyres used on each size... otherwise production would be a pain because each car would need to have the speedo adjusted for each wheel type...

[fredgroves]

There was this test:

https://www.tirerack.com/wheels/tech/techpage.jsp?techid=108

The difference roughly on that test was 2% mpg going up from 17's to 18's.

CO2 figures are largely directly proportional to fuel consumption, would ~2% account for the difference? I think it might...

[golfdave]

18" & 17" rims have 225 wide tyres as standard fit, & have the same overall rolling circumference (as near as), so no difference in aero drag, grip etc.

Weight of alloy & tyre makes the difference, as less wasted energy to get up to speed (drivetrain loss)

I purchased a set of TD PR1.2 for summer in 17" with 225/45R17 which is the same spec as my OEM factory 17" Dijon's...

Each one was 2.2 to 2.5kg lighter than the OEM alloys...

[Lock_r]

Yes, sorry, when I said the difference was only the wheels, its only the wheels which make the difference in CO2 emissions.

I've ordered the Blueline.
It's not just the wheels.  It has an AdBlue tank included as well I believe. 

The rest seems to be unconfirmed.  For example it's been reported the DSG box on the Blueline is now a 7 speed (same as the GTI), whereas it was 6-speed before (http://www.greenmotor.co.uk/2017/04/vw-golf-gtd-facelift.html).
So that combined with smaller "eco" tyres, is "supposed" to make the mpg marginally better, and "supposedly" less co2 emitted.

But some are claiming it doesn't really make a difference (the odd site says worse). 

I'm on build week 19 (next week).  So when i finally get my new car, I'll report back.