Les,
I get about 33 mpg combined city/highway driving. This was calculated
over 20 tanks of gas. I have gotten as good as 44 mpg on highway-only
tanks, but this is rare; my records show this happening twice and I
had been running the SUs quite lean. My highway speeds are about 65
mph.
My setup at the time of 44 mpg was stock 1.25" SUs newly rebuilt
(rebushed, new jets, new needles, etc), centrifugal advance only
dizzy, Pertronix Ignitor module in place of points, Valvoline full
synthetic 20W50 motor oil, and new Michelin MX4 145x13 tires expertly
balanced.
The items I am confident that helped with increasing my fuel economy are:
1. Rebuilt carbs, properly set. My records indicate that mileage went
from ~27 mpg to 29 mpg when I replaced the worn old set. The real
benefit, though, was smoother running and the ability to actually
tune the engine properly.
2. Full synthetic oil. This really surprised me. When I first added
synthetic, my idle jumped up quite a bit (I can't remember how much,
but I think it's in the archives). This prompted me to conduct a mini
tune-up, including timing and resetting the carbs (did not regap the
valve lash). I had done a full tune within the previous 1000 miles,
but the change with the oil intrigued me. Mileage jumped to 33 mpg.
3. The other changes may or may not contribute a darn thing.
Certainly the new tires make life better. The Ignitor was put on
because I felt like it. The centrifugal advance only dizzy was added
because it was what I had at the time that the old dizzy's bounce
finally pissed me off (shot shaft bearings).
Good topic, hope we hear from others.
Jeff
Jeffrey H. Boatright, PhD
Senior Editor, Molecular Vision
http://www.molvis.org/molvis
"Seeing the Future in a Very Tiny Way"
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