My 95 GT Vert is my only car. 17 in town, 22-24 freeway. I don't put a lot of miles on it so although the price of gas has affected me some, it hasn't killed me yet.
To me it makes no economic sense to spend hundreds, if not thousands, on a beater or other car just because it gets better mileage. If nothing else, the extra insurance costs will negate the minimal amount of money you'll save on gas. Do the math yourself.
But to help, assume you drive 12,000 miles a year and average 20 mpg on 87. 18 months ago gas here was $1.36 here a gallon. That's $876 a year, or $68 a month.
Today it was $2.27 a gallon. Using the same numbers, that's $1362 a year or $113.50 a month, an increase of $45.50 a month.
Using these numbers, does another car make sense? I don't think so.
On the other hand, if you need something else to drive in winter's snow and ice, that's a different issue altogether.
Just my $.02.