Flush Systems: A Big Taboo.. This info is from a Honda service news of 2006

In Honda vehicles, the transmission, as well as the
systems that handle lubrication, cooling, fuel, and
power steering, are designed to give thousands of
miles of trouble-free service if you follow the
maintenance schedule to the letter.

Flush systems are a popular aftermarket offering
these days. These products look impressive and
make lots of claims, but American Honda strongly
recommends you avoid using them on any Honda
vehicle.
Here’s why:

• The maintenance schedule neither requires
nor approves of aftermarket flush systems.

• Flush systems take time to do; this adds to
your service customer’s wait time.

• Flush systems haven’t demonstrated an
improvement in vehicle performance or
reliability.

• Flush systems using solvents may leave
solvent in the system you’re flushing. This will
dilute the fluid or lubricant and degrade its
performance.

• Flush systems using filters can filter out vital
additives and degrade the fluid’s or lubricant’s
performance. This is particularly true for
coolant.

• Any damage caused by flush systems isn’t
covered by warranty.