GTI highway fuel consumption. A roof box, a hill and cruise control

[nabes]

I had to visit Canberra last friday and today for work, and my golly gosh what a boring drive it is. So to keep me entertained aside from listening to music I have done some unscientific statistical analysis of my journies.

GTi Mk5 is stock 6-speed manual with 20k on the odo.

All stats from the in car MFD. Comparisons with different speeds on the Cruise control and the effects of a roofbox. The roofbox was still on the car from our Easter trip.
Note: The journey started in North Rocks and the closest height measurement I could find was for the North Parramatta weather station which is listed as being 55m above sea level. Fyshwick, the final destination is listed as being 579m, so it would be anticipated that more fuel would be used in the Sydney --> Canberra leg since I was driving half a kilometre up hill.

Trip 1.
Sydney --> Canberra
With Roofbox on top; Cruise Control set to an indicated 120 km/h
Result: 8.4 L/100km

Trip 2
Canberra --> Sydney
With Roofbox on top; Cruise Control set to an indicated 115 km/h
Result: 7.0 L/100km

Trip 3
Sydney --> Canberra
No roofbox, Cruise Control set to an indicated 115 km/h
Result: 6.4 L/100km

Trip 4
Canberra --> Sydney
No roofbox, Cruise Control set to an indicated 115 km/h
Result: 6.2 L/100km

So Canberra --> Sydney saw a drop of 0.8 L/100km for the removal of the roofbox. A reduction of 11 %.
Sydney --> Canberra saw a drop of 2.0 L/100km for the removal of the roofbox and a 5 km/h deduction in speed. A reduction of 24 %

Working on a percentage basis ... and considering all variables are the same, (which no doubt they aren't and in no way is this experiment scientific)
If only the roofbox had been removed and a speed of 120 km/h had been maintained then a reading of 7.4 L/100km would have been achieved (working to 1 decimal place, as this is what the car measured)

So what has the greatest influence? The roofbox or the speed? It is about the same. What a massive difference though on my first and second trips sydney --> Canberra. And what an amazement that a 2.0T sports engine can achieve 6.2 L/100km on a freeway drive. Who needs a diesel or a hybrid? Especially when the GTi can actually do corners too. The car for all seasons.

There you go. That kept my 12 hours of driving interesting ... what a boring sod I must be. At least this friday I get the chance to drive to Bathurst over the Bells line of road and back. Fuel consumption won't be the consideration then!

Nabes

[jessv3]

Nice finding, I travel up north to newcastle quite a lot and my 6spd manual GTI seems to get about 7.8/100kms i sit on 120kph the entire way though and from memory the F3 is a lot more hilly then the trip to canberra. If i really tried i reckon i could bring it down into the 6's.

Another variable to chuck in as well is servicing, I got my car serviced when i was up in newcastle on the weekend and i noticed a drop of .2L in my fuel consumption on the way home, I know this could of been contributed to other things but it was a drop none the less.

[soogs]

Nabes u're a legend, my kinda guy, don't let anyone tell you you need to get out more.

Didn't realise such a difference 5kph makes to the consumption even allowing for the roof box.

[Maverick]

Trip 3
Sydney --> Canberra
No roofbox, Cruise Control set to an indicated 115 km/h
Result: 6.4 L/100km

Trip 4
Canberra --> Sydney
No roofbox, Cruise Control set to an indicated 115 km/h
Result: 6.2 L/100km

Next time you do the trips you should do one trip with the car unwashed and dirty and the next trip with a fresh coat of wax (do a quick detail in Canberra).

[docjames]

Interesting comapro, thanks for posting.

Speed makes a huge difference to any car's fuel useage.

Also figure on about +5% for every 100kg weight added. Presume the roofbox was empty so mainly aerodynamic drag. good numbers, I seem to be in the low 7s cruising Bris to Gold Coast or SUnshine coast varying indicated 108-118kph (pending speed zone, my speedo ~10kph out at those speeds) and can squeak into 6s at the lower cruise speed.

[EUS GTIMK5]

Did a similar trip, Melb to Canberra and back. Used GPS to set speed to a couple of Kmh below limit (to be safe). I averaged 7.7l/100km. Again shows the type of economy you canget on a highway drive. Just love the car, great when you hit the overtaking lanes!

[MariusGT]

not a GTI but on a similar drive (sydney -> bega) i averaged 6.7 with cruise set to 110

my best tank was a trip to thredbo last year where i made it there and some of the way back before i had to top up.

notched up 820kms before piking and filling up.

is cold climate a contributing factor to good fuel consumption??.....

[weiero]

awesome..... lowest ive got is 6.4ltr / 100....... on 110km/h. LOVE IT