In Ontario, we have the option of purchasing gasoline that has a number of additives already in it:
http://www.sunoco.ca/content.asp?id=153
Started using this with my 1st fill up so don't have any comparative figures. First 2 tanks are both just above 20mpg, with about 95% of the exact same route for each tank and conservative driving style both times.
(added note: 50% freeway at 65 mph, 45% highway at 55mph, 5% city)
Not sure of the exact amounts used, but I'd guess the quality of the additives is very high.
You can also purchase gas coupons online and get free car wash coupons as a bonus. (free shipping on the coupons)
[ 10-20-2002: Message edited by: HDLD ]</p>
2003 Silverado 2500HD D/A CC/SB LT 4x4, Camping Mirrors, Skid Plates, Lund Cold Front, Phillips Premium bulbs, Fumoto drain valve, Mobil Delvac 1, TranSynd ATF, Line-X, MagnaFlow 4\" catback, Amsoil air, Bilstein Shocks.