My numbers
97.5 Regal GS K&N stock replacement
AVG: 22.8 (60% highway, 30% city, 10% waiting in line to get on base)
Highway: 28.4(AC on), 29.8 (AC off)
City: No real good idea as I'm never off the freeway that much
All 97.5-2004 Regal GS's are supercharged, some of the earlier ones were too but they used the smaller M62 (62cid) Eaton blowers not the M90 (90cid) blowers of the later engines. If you are looking for a daily driver, even though I'm thinking of selling my 97.5, get a 99 or 00 as they fixed many of the problems that the 97.5 and 98 had and added some nice features while still having most of the fun controls in the hands of the driver instead of coded into the computer. If you're going racing get a 97.5 or 98 since they are the lightest.
Just my owners comments,