Hi Digitalfix,
I use mine for a 40 mile each way commute in the UK. It is mainly motorway (freeway) and if I keep the speed down to 55/60 in the warmer weather I can get 95 to 100 mpg (US gallons). My average over the 3,000 miles so far is 82.3 Mine is only slightly modified, with a radiator air blocking sheet and the tyres pumped up to 55 PSI. (get new Bridgestones as the ones on the car are probably too old for safety...PM me if you need to know how to check tyre dates)
When I get my MIMA and the weather heats up I am expecting greater things. Whatever you end up with, you will be well pleased, but you WILL end up driving slower than you did, and you WILL start tailgating trucks
I would recommend getting a Scangauge Mk 11 so you can get a true engine temperature reading and see leanburn (if the car is a manual version) the Scangauge fits a treat in the cuby box below the radio...you only have to make one small hole in the "roof" of the cubby box for the cable and the hole will never get seen by any later owners....
Rog