[onu2002]

I didn't mean that Honda "requires" a thorough flush, but that the 4x procedure is required to perform a thorough flush.

The manual says "the transmission should be drained and refilled with new fluid" according to the schedule, but doesn't explicitly say 1x or 4x. I guess you could infer either, but 1x is probably correct, since it explicitly recommends 4x after using non-ATFZ1 fluid.

I'll probably continue the 4x, since the added cost and effort doesn't really amount to much since it takes me about 3 years to go 30k miles.

And I don't think 4x would be required for VTM4, since the diff is self-contained and the drain is at the low point.