2100 with a 289 and MPG

Hi guys,

After a 2 years full restoration of a 66 Mustang convertible I'm a little worried about my gasmilage. I have a standard rebuild 289 with an autolite 2100, c4 automatic and 3.00 open diff. I only get 12 mpg with this combination which is a bit high to my opinion. I drive 50% city and 50% highway at 60-70 mph.
I've rebuild the carburator and replaced the 58 size jets for 50. The carburator has the 1.14 stamping, C5ZF-B part number and everything looks normal and works fine. Choke symstem works fine and doesn't stick, no black smoke and good accelaration. So is this 12 mpg OK for this combination or can it be much better? If it can be better what could be the cause for this milage?

Thanks,

Erwin, The Netherlands