well.. "grit helping it shift" is a new one on me.... personally at 235K I would do a series of pan drop changes.... eg. drop the pan, change the filter, top it up (about 1/4th of the fluid will be new....) do it again in a few thousand miles.... repeat 3 times over about 6,000 miles before you do a complete fluid changeout.
See you really don't save anything by delaying a fluid change! (grin)