I have the same vehicle model with a 45RFE trans. If the overdrive is turned off or not functioning gas mileage will be about 12/13 mpg. With overdrive engaged mileage 18/24 mpg should be obtained. Normally overdrive is engaged when truck starts and must be manually turned of for pulling trailer, etc. (Button is on end of shift lever.
Monday, December 8th, 2008 AT 1:45 PM