Don Kirkman wrote:
It seems to me I heard somewhere that Frank Slootweg wrote in article
e.nl:
[...]
The extremes were on highway 395, probably somewhere between where
89 joins from the west and Bridgeport in the south. Next time I'll make
pictures! :-)

Western geography has a large effect on gas prices. The northerly end
of the Sierras is sparsely settled and prices will tend to be
higher--higher hauling costs and fewer gallons sold. From about
Bridgeport south you come abreast of the state and federal parks
across the mountains (Yosemite, for instance) and have more and larger
towns, hence more traffic. This may account for lower prices

Your explanation sounds very plausible! I *did* think about the
sparsely settled/isolated aspects, because we're used to that from our
travels in Oz ("Did we see a car today?", "Yes.", "Wow, this is a bloody
busy road!"). But I thought, different places on one and the same road
shouldn't make any difference. But I didn't think about the *crossroads*
(especially because some/most of them - noteably the Yosemite one and
the one just above - were closed at the time).

Thanks.