I'm preparing for a trip out West from NC with a recently purchased 29 ' used 5th wheel. One of my preparations is to install the Mag-Hytec 727-DD transmission pan. My quex. s concern transmission fluid. I went to Advance Auto Supply to check on fluids. Their brand of ATF+4 costs $4/qt. Castrol ATF+4 synthetic cost $5. 25/qt. Mag-Hytec sells LE 7500 Monolec power fluid for $6. 20/qt. (+SH) but Cummins diesel is not one of the brands listed for use. I called my local Dodge dealer and they want $8. 25/qt. Has TDR ever done an article on transmission fluids like was done on motor oils? Is Mopar that much better or is this an example of dealer markup? Any idea why there is so much variability in the price?