Please settle a dispute for me, sounds like a stupid question, but bear with me... For those of you familiar with driving a Dodge 6 spd manual H/O turbo diesel. At what gear should you be in at 50-55 MPH? 5th or 6th? Thanks.

yup

Depending on whether or not you are towing, or running empty, or going up a hill, or or or

5th or 6th is fine. Just revving a bit more in 5th

Yeah, I reckon I should have been a bit more specific, realized that last night after I got offline. Specifically... no load, normal highway driving with no huge inclines, etc...

running empty there is nothing wrong with 6th. running loaded, kep it pulling above 1700 rpm. which means 5th from time to time

MPG will suffer over 2000rpm, too.