The flushing procedure on the manual of our 04 Accord says to drain and refill 3x and then drain and refill a final time, so 4 times total. It also says you can use DEXRON III as a temporay replacement but then you need to do the flush procedure with the Z1 fluid. I did a drain and fill at 20k miles and just now I did a drain and fill again at 40k miles with honda Z1. I'm thinking of doing this every 20k miles but switching to castrol import atf in the future. does anyone see a problem with this??