I had a 95 Monte Carlo with a 3.1 and 4th went out. On the hiway the RAMPS would be around 2k, and when it stopped going into 4th, it would run around 3-4k RPM. I dont have exact fuel numbers, but a 120km run doing 120km/h would use about 1/6 a tank, and after 4th went out, the same run would use like 1/3 a tank :\