capacity is ~4.5l.  can only drain ~1.5l at a time.  the change is
therefore achieved by "dilution".

even just one change makes a difference - it removes a lot of the crud -
but it can never be the whole solution.

The service manual addresses a simple change as being a drain/fill
procedure, but it also (at least newer manuals) talks about a complete
replacement as doing the drain/drive/fill multiple times.

On 1/13/07 11:31 AM, in article
2I8qh.58517$qO4.21531@newssvr13.news.prodigy.net, "Bob Jones" <email@me.not>
wrote:

The Honda book doesn't say it needs to be done more than once. The FSMs on
my Nissans both give the same advice: drain it, fill it, drive it, check it.
Repeat until it is the right color and smells right, up to three times.
This makes as much sense as anything I've seen on the subject.

That is commonly accepted as the number of times it takes to pretty much
completely replace the fluid.

When you drain it, there will still be a significant amount of fluid in
the car.  You are looking to dilute it to be close to original formulation...

The owner's manual says to do it once, and that's what the service
schedule is intended to accomplish.

The "drain and fill 3 times routine" is mentioned, but this is
specifically to get rid of contamination caused by using non-Honda
fluid.  At that point, you do have to get the majority of the fluid
out.

That's what the Honda shop manager told me when I asked about this.
They only drain and refill once for a tranny fluid change, in other
words.

That's probably enough in most situations.  There are plenty of people
doing more, and I'm marginally one of them.  Let the appearance and
smell of the tranny fluid be something of a guide.

My Accord V6 has 28,000 miles and the fluid looks and smells almost
like new.  That means one fluid change is all it's getting until it
gets considerably more miles.

My MDX has 28,000 miles also, and the fluid smelled somewhat nasty and
was turning brown.  The first time I changed it at this mileage, the
appearance really didn't change, it still looked bad.  The second
change (6 miles later), it looked pretty good.   Now I'll wait until
the end of the summer heat and change it again.  And, then probably put
it on a 15,000 mile routine for a single drain and fill as long as we
have it.

Remember, you get a higher percentage of contaminants out at higher
mileage because they've built up more (so each change makes more of an
impact, percentage-wise).  It makes some sense to change it fairly
often after 45,000 or 60,000 miles.  But not much sense to change it
very often before then.  You're only trying to dilute the contaminants
to a reasonable level.  That is, you're diluting the contaminants to
what the transmission would have at, say, 30,000 miles.  Each change
after that brings the total contaminants back in line with that 30,000
mile baseline.

Or you can change fluid like crazy and perhaps achieve a 15-20,000 mile
baseline.  But the dilution method will never get you even 80% much
less 90% "new" fluid, and the tranny doesn't need that anyway.  The
math is an interesting study in futile maintenance.  Each successive
change gets about 40% of the remaining contaminants out, so the law of
diminishing returns sets in pretty fast.