<VV> Tire Sizes and MPG

[Rex Chivers]

I am running 185 60 14 tires on my vair.  I get around 17 mpg around town. 
My vair is a 65 convertable with a 95 hp with Pg.  My friend has a 65 coupe 
110 with 4 speed and gets 22mph around time.  He is running 185 80 14 tires. 
I like the way my car looks with the lower profile, but with gas prices I 
have to wonder how much the tire size might affect the fuel economy.  I know 
when I am running 70 mph indicated it is actually running about 64 mph true. 
This is consistent with the different circumference of the two tires.  I 
recognise that the standard will get better milage but it seems like quite a 
bit of difference.

Any thoughts or past experience with tire diameter and milage ??

Thanks
  -R-