Ummmmmm - how about shutting it off going down hills and at traffic lights? Seriously, 10 mpg sounds way off the mark even in a 79 Caprice. Before panic totally sets in I would go over all of the usual tune up details such as timing, condition of distrib cap & wires, plugs, etc. Making sure everything is as right as it should be. Don't overlook things like correct tire pressures, dragging brake pads and shoes, automatic choke settings, and a possible carb internal leakage if the plugs are showing sooty.
Unless the car is being driven with a couple of bricks glued to your shoe I have to think it ought to give you around 13 - 14 mpg even in local driving if everything is right.
Mike G ( 4355 )