The very best you will get is 17 city and 26 highway, but on a 22 year old car you will more than likely be lucky to get 15 city 24 highway.
A 1991 Chevy Suburban will get 11 miles per gallon if driving in the city. It gets around 15 miles per gallon on the highway.
There is no trunk release on a 1991 Chevy Caprice.
about 25 US gallons depending on the year. I HAD A 1991 CAPRICE POLICE PACKAGED. IT HAD A 23 GALLON TANK. My 1991 Caprice (Plain jane, rounded version) has a 23 gallon tank - I imagine it's the same for the "Classic" edition. Hope that helps some - Kenny
Yes you can.
Yes. 1991-1996 springs are interchangeable.
Depends on which engine it has. Try a Google Search.
yes
No
15 city and 19 highway.
yes
Yes, several.
700 r 4