fuel consumption

[John&Sene Johansson]

Hi There
This is about our every day car, a Nissan Prairie 2,4 L Automatic.
I am driving around 50-60km/day(same road and queues everyday) and i have a
habit from the old country to keep an Eye on the petrol consumtion(as the
price was $2,50/l). Another old habit was that I always used the local Mobil
station.
The consumption has been around 11l/100km or 1.1l/10km not bad for a car
like this.
But I think 2 months ago It was a local "pricewar" here in South Auckland
and GULL had a really good price so I filled up the Nissan with Gull 91.
Next time I filled up, the consumption had dropped to 1l/10km 10% less, so
now I have swapped between Mobil and Gull a couple of times and Gull is
always coming out with a lower consumption.
So in a year I would save $250,00 (that's allot of Thomas the tankengine
toys for Erik).
The only explanation I have is that Gulls petrol is sourced from overseas so
maybe the energyvalue is higher compared to the petrol from Marsden Point?

John Johansson