What is the miles per gallon for a 5.7 liter V 8 1994 Chevy g 20 van?

Lots of things to factor in on such a question- mileage/condition of motor, rear end gear ratio & driving habits to name a few. I have a 1995 G20 Gladiator Conversion van 114,000 miles 5.7 4L60E 3:42 gears - Maintained like its the last one on Earth. In town 11/12 mph out on the hiway family with me cruise set at what ever the speed limit may be and have gotten 15/16 mph. Bowtiefan