Did the second of my twice yearly 880mile round trip last week.

Normally cruise set at 70mph car averages 35mpg....

The road conditions were almost the same as my last trip but this time , even though car was laden with approx 50kg extra luggage the same trip with cruise set at 73mph resulted in 38mpg.

Fuel was same brand and grade.

Only things that have changed are:

..DSG oil change,

..Two rear Dunlop tyres change to Conti2's which match the fronts.

..Added a boot gauge.

All I can think of is 73mph is a good "sweet spot" for mpg.....

The oil change and the new tyres (higher pressure?) sound like the more probable cause? Or different air temperature/density? Just a guess, but 3mpg is hardly significant (~8%?).

That's too small a difference to be statistically significant especially when comparing just two runs.

The changes you mention can have an affect , as can humidity and temperature , driving style , wind direction and so on.

LLOL at Zoidberg's new sig! Fight the power!

Curiously, I discovered that very same paradox this week but mine's a 2.0 PD DSG. I left a bit later than I should to do a 100m trip on M/ways and Dual/Cs. I normally trundle along at 70 - 75mph (as indicated on satnav) and get about 47 mpg on the computer. On this particular day I was in a bit of a hurry and putting my foot down without worrying about the mpg (I just needed to get there). I regularly did 80 - 85mph.

And got over 50mpg...

I think my relatively light foot could be heavier.

dill

My interpretation of this black art is that you spent more time in 6th gear by travelling at higher speeds , IMHO . When you did have to slow down you were more likely to remain in 6th gear - this to my way of driving appears to be the critical factor . There is perhaps also a large difference between cold and warm weather driving .

Warm weather gives me better economy than cold weather, and dry roads are better than wet. Also some days I am more aggressive with the acclerator than others, even though my nominal crusing speed is the same (ie on the speed limit).