A1 GTI speed and fuel consumption experiment results

[Simon C]

Dear All

Yesterday I was travelling home from Sunderland to Keighley, West Yorkshire to my parents for Christmas. I was driving in the afternoon and the roads were reasonably quiet, so I thought it was a perfect opportunity to experiment and play with the Adaptive Cruise Control at different speeds and see how the GTI responded in terms of fuel consumption. At all times the GTI was set in normal mode.

Here are the results:

Part 1: ACC set at 75 MPH for 10 miles - Actually averaged 74 MPH and achieved average 29.4 MPG.

Part 2: ACC set at 70 MPH for 10 miles - Actually averaged 69 MPH and achieved average 35.5 MPG
.....so far the results seemed sensible enough.

Part 3: ACC set at 65 MPH for 10 miles - Actually averaged 65 MPH and achieved average 35.2 MPG
.....could not believe this, can only put this down to gradually climbing uphill. So I repeated it....

Part 3 continued: ACC set still at 65 MPH for another 10 miles - After 20 miles now averaged 65 MPH and achieved average of 35.1 MPG........still shocked, so extended it again.

Part 3 continued again: ACC still at 65 MPH for another 7 miles - After 27 miles now averaged 65 MPH and achieved average of 35.9 MPG......so starting to improve. Think this was down to less climbing.

I then got bored of getting overtaken by old folks, white van men and others who wondered WTF I was playing at. So I stopped at Wetherby services for a pit stop. Photos below:





Then back on the road.

With only 2 miles of motorway driving left I had completed about 90 miles and averaged 37 MPG over the latter part of my journey from Wetherby to Bradford, this typically involved me driving in ECO mode and averaging about 63 MPH due to heavy traffic. I was still typically in ACC mode and was being careful with speed etc.

Overall the drive was pretty frustrating due to driving at a snails pace. So I decided to end on a high by sticking it in to SPORT for the final 2 miles on the M606 that takes you into Bradford from the M62. Wow - that was fun! Foot down and a great blast and a great noise and growl from the GTI who just chewed up the motorway. However the blast took its toll on fuel with the average dropping from 37 MPG to 32 MPG within the space of 5 mins or so.

Overall an insightful little experiment as fuel was an important consideration when I bought the GTI. Hopefully some of you find the observations of interest. My main conclusions:

1. If fuel / cost is of any importance then motorway driving needs some consideration with the GTI as I get the impression if I was consistently at 80-85 then I could have been at mid-20 MPG. Which is pretty poor. Would be interesting if any of you guys disagree.

2. Driving consistently at 65 MPH is boring as hell....though quite entertaining for other car enthusiasts who wondered what the hell I was doing.

3. ACC is cool!

I know some people may reply and say 'if you are bothered about fuel / cost then you should have got a GTD'. I understand that, however for me I still need to have an eye on the fuel bill so this bit of experimentation was useful.

Best wishes and merry Christmas all.

Si

[Mr Savage]

ACC is very detrimental to MPG. Your'll achieve much better MPG with it turned off.

The GTI is economic when driven in Eco mode very slowly. I averaged 41MPG in a DSG using Eco mode and the speed limiter set to 60.

The GTI is incredibly thirsty when driven fast, the fuel gauge will plummet. I imagine you can get through an entire tank of fuel with foot to the floor action in just 150 miles.

[Simon C]

ACC is very detrimental to MPG. Your'll achieve much better MPG with it turned off.

The GTI is economic when driven in Eco mode very slowly. I averaged 41MPG in a DSG using Eco mode and the speed limiter set to 60.

The GTI is incredibly thirsty when driven fast, the fuel gauge will plummet. I imagine you can get through an entire tank of fuel with foot to the floor action in just 150 miles.

Thanks for comment Mr Savage. On my way back north on Friday morning I might test it again at 65 MPH but avoid ACC...cheers for the pointer.

[monsta]

Mine seems more economical at 85 than 80.  I leave it with everything on sport except engine which goes on eco and suspension which goes on comfort for the motorway.

Only noticed this at 1000 miles onwards was poor before that.

[legg360]

On my mk6 GTI, if I sit with cruise control on at 60 I can ave a decent 47mpg, but between mine and Cheltenham there a few miles of twisty A/B roads and ill ave 14mpg

Sitting at a slow speed can be boring but the extra time in a journey isn't that much longer for the amount of fuel saved so I think its worth it

[mcmaddy]

acc isn't detrimental to fuel economy at all. pretty much the same results using it out not.

[monkeyhanger]

acc isn't detrimental to fuel economy at all. pretty much the same results using it out not.

Depends on your definition of detrimental. It will always be a little worse than manual control, in a manual at least because there are times where it will brake the car to maintain a speed rather than allowing it it climb a little temporarily when going downhill etc, sapping your momentum, or braking when the ADC sensor determines the car in front is too close when you might otherwise just cover the brake (just in case) and come off the throttle to allow the gap to open up again.

Not really made use of it more than a few times myself as i've not done a really long journey (over an hour at motorway speeds) in mine yet.

Once the car is up to temp and the car is travelling on the motorway, my dad claims his fuel economy dips 5%/2.5mpg with it on for a longer journey, although he does have DSG and the coasting function is likely to mitigate some of the CC losses when he puts his in eco mode.

Best used in situations where throttle is pretty much constant like maintaining a speed on a non-busy motorway (and braking is minimal) rather than trying to maintain a speed on varying roads and having the system brake and accelerate a lot.

[Simon C]

[/quote]

Best used in situations where throttle is pretty much constant like maintaining a speed on a non-busy motorway (and braking is minimal) rather than trying to maintain a speed on varying roads and having the system brake and accelerate a lot.
[/quote]

Im taxying my mother to Blackpool to see some family today - I will try what you have suggested and see how I get on. I'll let you know.

[Mr Savage]

acc isn't detrimental to fuel economy at all. pretty much the same results using it out not.

It really is. Exactly what Monkey Hanger said. Doing it manual has always been the most efficient. The car will always accelerate to try and maintain speed when a human will not mind the car dropping to 55 for a moment and then the momentum of the car (when it coasts) pushing it up to 60 again.

[2014GTi]

Any form of cruise control is worse off that manual control.
I tested it in my Polo Bluemotion using just cruise.