Over the past ~3 weeks I've noticed a slight drop in power & mpg for my
Westy (what power you may ask?). Specifically it feels like i'm fighting a
headwind on the freeway at 50 - 60 mph.
Searching for answers and hoping it is not a real engine problem (this 2WD
Westy has 195k on the original engine), I followed a hunch on gasoline
formulations & found the following;
- the winter gasoline formulation for California has an average of 1.7%
lower energy content (vs. summer) - due to added butane
- the changeover date is Oct 31st (most stations switch over a little
earlier)
- other factors that affect fuel economy include air temperature (the
daytime temperatures have dropped significantly over the past two weeks
here)

http://www.afdc.energy.gov/pdfs/2876.pdf

Having read all this I am less worried that the engine is on it's last legs
(I still have no really good excuse to spend large $$ on a new engine...)
--
Mike Hart
Palo Alto, CA (SF Bay Area)
1987 2WD White Westfalia GL 'T3Westy'