Howdy folks, 
        Just some observations from a long running experiment. My 91 with
auto trans has historically averaged about 17-18 mpg in town. During this
time, the temp guage never deviated more than a needles width or two from
the led in the middle. About three months ago, the temp gauge started
showing my van running relatively cool. The needle *never* even got close to
the led unless I let it idle for ungodly amounts of time. And even then, as
soon as I started in motion, the gauge would shoot back into the 'cool'
range. I assumed my thermostat was stuck open but didn't swap it out for
about two months. During this two month period, my average mpg was about 13-14.
        About three weeks ago, I finally swapped out the thermostat and this
corrected the cool running problem (the thermostat was NOT stuck open,
however, a qualitative test on my kitchen stove revealed a relaxed
spring-opened sooner, and closed later than the new thermostat). After two
tankfulls, my milage is back in the ~17mpg range.
        An explanation? I'll leave that to someone who actually knows what
they're talking about. All I know is what I saw :)

Sincerely,
Pat
        
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Patrick L. Larsen
Water Center/Environmental Programs
University of Nebraska
pll@unlinfo.unl.edu
http://www.uvm.edu/~plarsen/pat.html
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