just because educated car owners are cooler i must give some auto theory behind this question, ok the primary difference between the fluid in a manual tranni and an automatic is that the automatic fluid is actualy a variant of hydraulic fluid and your manual uses lubrication-type oil to simply keep the gears and related assemblys slick(an automatic tranni uses the fluid to shift via hydralic pressure). both fluids need to be changed every once in a while im not totaly positive on the mileages for either but id think like every 50-60k for an automatic and maybe a little sooner for the manual.