mpg puzzler

["Shaun D. Mullen" <smullen@philly.infi.net>]

My '92 100CSQW gets somewhat better gas mileage at 180K than it did
fresh off the boat, but the results I got last weekend on an 830-mile
roundtrip drive between exurban Philadelphia and Chapel Hill, NC, were
surprising.  I typically get about 23-24 mpg on the trip (a couple mpg
less from November to March when oxygenated gas is required here in the
Northeast US).  I average a little over 60mph on the route, except in
bad weather and very heavy traffic, neither of which I had this past
weekend, and my gas mileage has seldom diverged from that 23-24 mpg
range the many times I have made the trip using an identical, largely
interstate highway route.

This past weekend, my gas mileage ranged from 25.6 to 27.3, a 2-3 mpg
increase.  Any suggestions or theories as to why this healthy jump in
mpg occured?  I won't be making the trip again until later in the
summer, and will be unable to test until then whether this trip was an
anomaly, or my quattro is just beginning to enjoy old age.

-- Cheers, Shaun