I do not have access to a mechanic close enough to check the sensors.. however I read about the codes and flashing check engine light.. can one find the information about oxygen sensors, and other sensors responsible for fuel consumption? I have a 1991 dodge ram PU, 250, 5.9 4WD. Auto, really clean, well maintained. But it gets 7.5 mpg.. ouch... plugs are nice color, uses no oil. great power, check engine light is not on... I'm new to Dodge trucks, just inherited this one from dad..

 

https://dodgeforum.com/m_63384/tm.htm

 

Hi, I live in Longmont, I see you are from Fleming? Shot my first pheasant ever out near Paoli!
Your 91 has TBI(Throttle Body Injection) fuel injection. You could have a leaky injector, there are 2 injectors in the TBI but I would start with the basics.
Complete tune-up, air and fuel filters, oxygen sensor should be changed every 60K miles, Coolant Temperature Sensor(CTS) helps control air/fuel mixture, when you are in NAPA or CarQuest pickup a can of SeaFoam and run it through the gas tank..it's good stuff. www.seafoamsales.com
Run the error codes using the key on off procedure in the above post and see what codes, if any, come up.
How many miles on this truck?