Minimum miles between drain & fills?

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I will be doing multiple (4) ATF drain and fills on a car with dark fluid.
How long does it really need to be driven between each d&f to be fully mixed?
I'd prefer to just leave the ramps and tools out and do all 4 d&f's over the course of a week.
I would *think a couple 10 mile trips would be sufficient to thoroughly mix, but admittedly, I have no idea how much ATF really moves around...and I see sooo many recommendations to wait 500 miles or more between each d&f.
 
You should be good by way of mixing by driving 10 miles between drain and fills. However it is recommended to go around 500+ miles to gradually introduce the detergents/dispersants along with the fresh additives. If the fluid is still relatively fresh and just dark in complexion (along with a well maintained transmission) then there shouldn't be a problem with the 10 mile runs to swap all the fluid out. Have you considered a cooler line flush?
 
Ah, I see.
Well, it's a 2012 4cyl Accord with 105,000 miles.
Shifts perfectly. We've not owned that long. Previous owner maintained the car well and claims the ATF was serviced "regularly".
The ATF doesn't smell burnt, but sure is dark...much darker than our Toyota's get after 40-50k miles. Anyway, being an Accord, I prefer the d&f route to a flush.
 
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My theory, it should be a combination of time driven and time sitting. Like take it to work and back for a week or two, fluid can circulate rather quickly but also the hot/cold cycles and sitting will help the new fluid get the dirt out.
 
Dissenting opinion.

Once around the block is sufficient to mix the fluid. It is constantly pumping through the transmission and isn't going to take long to mix. By the time you back it off the ramps and out of the driveway, and then drive a few miles, it will have circulated through the valve body, solenoids, and torque converter.
 
Why don't you try this...just do one drain and fill, then do another a few months down the road...then another...then another. Then there is no question about how much is mixed and how much is not, plus it'll be a much more gradual procedure. And seeing as how you just bought the car (or not owned it that long), if something were to happen because you changed all that fluid at once, with just one drain and fill no one could say...well look, you flushed all the transmission fluid, it's your fault (I don't think anything would happen, but doesn't Honda recommend one simple drain and fill every however many miles?).

I took a Honda Accord 289,000 miles by doing a simple drain and fill once a year, without one single transmission issue (and my car had a class action suit against Honda because of transmission failure). Was still running and shifting fine when I sold it.
 
When I did the same for 2006 Sentra 3 years ago (same mileage), I was told on multiple discussion boards that it should be done once every month. I did 3 such drains and refills over the summer. My car wasn't shifting well between 1st and 2nd (used to get a hard jerk) but this resolved the issue to an extent.
If you don't have a garage, I understand why you prefer to do it in a week.
 
Once you get it through the gears its mixed. If I buy a car that has old or dirty ATF I run one dump 50 miles or so and then a do a full 100 flush if it has a cooler line.
 
I would wait until you change your oil next time. If you have not had any problems with the transmission and it shifts ok you will be fine waiting until the next change. If you really want to change it early I would go 20 miles and drain/fill. I change my Civic's AT once per year and use only the Honda recommended fluid. That is one thing I really like about Hondas is the fact that it is so very easy to do yourself. My son has a 2012 Honda Civic as well and we changed it for the first time at about 65,000 miles and he has over 100,000 on it now and still hasn't changed it. Some of these millennial's are not too prompt on maintenance. I will be seeing him today since he is out of state usually and remind him to do it.
 
Obviously the fluid gets pumped around.

What nobody seems to know (or even mention) is how fast fluid exits the torque converter under normal operation.

I've read that dirt accumulates in the TC. I saw no proof of this.

If the TC doesn't "drain down" upon shut down it'll be full of older fluid for a while. Sorta like taking a glass milk bottle full of one fluid and dribbling some other fluid onto its brimmed opening. How long would complete mixing take?

I've made this comment several times in these "How long between drain & fills" threads and no body ever responds with any TC drain down knowledge.
 
Originally Posted by Railrust
Why don't you try this...just do one drain and fill, then do another a few months down the road...then another...then another. Then there is no question about how much is mixed and how much is not, plus it'll be a much more gradual procedure. And seeing as how you just bought the car (or not owned it that long), if something were to happen because you changed all that fluid at once, with just one drain and fill no one could say...well look, you flushed all the transmission fluid, it's your fault (I don't think anything would happen, but doesn't Honda recommend one simple drain and fill every however many miles?).

I took a Honda Accord 289,000 miles by doing a simple drain and fill once a year, without one single transmission issue (and my car had a class action suit against Honda because of transmission failure). Was still running and shifting fine when I sold it.


+1 on this. On my 97 Civic I usually do a drain and fill every 2-3 years. It's only driven 6-7K miles per year. I'm using Maxlife ATF on the Civic.
 
Originally Posted by lukejo
I will be doing multiple (4) ATF drain and fills on a car with dark fluid.
How long does it really need to be driven between each d&f to be fully mixed?
I'd prefer to just leave the ramps and tools out and do all 4 d&f's over the course of a week.
I would *think a couple 10 mile trips would be sufficient to thoroughly mix, but admittedly, I have no idea how much ATF really moves around...and I see sooo many recommendations to wait 500 miles or more between each d&f.

You mentioned ramps and tools. I don't know what car this is in but I use a Flo N Go setup utilizing a shop vac and 3/8 OD plastic tube to vacuum out about 1/2 the fluid from the dipstick tube. You can space out the extractions over a few weeks because it is so easy to set up the shop vac and Flo N Go jug.
 
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Originally Posted by lukejo
Ah, I see.
Well, it's a 2012 4cyl Accord with 105,000 miles.
Shifts perfectly. We've not owned that long. Previous owner maintained the car well and claims the ATF was serviced "regularly".
The ATF doesn't smell burnt, but sure is dark...much darker than our Toyota's get after 40-50k miles. Anyway, being an Accord, I prefer the d&f route to a flush.


I had a 2010 Accord 4cyl and I changed 3 qts every 20k. I even used a roto zip and made me a open space so I didn't have to drop the plastic belly pan each time. Overall this will give you fresher atf than doing it every 60k like Honda recommends.
 
Originally Posted by Snagglefoot
Originally Posted by lukejo
I will be doing multiple (4) ATF drain and fills on a car with dark fluid.
How long does it really need to be driven between each d&f to be fully mixed?
I'd prefer to just leave the ramps and tools out and do all 4 d&f's over the course of a week.
I would *think a couple 10 mile trips would be sufficient to thoroughly mix, but admittedly, I have no idea how much ATF really moves around...and I see sooo many recommendations to wait 500 miles or more between each d&f.

You mentioned ramps and tools. I don't know what car this is in but I use a Flo N Go setup utilizing a shop vac and 3/8 OD plastic tube to vacuum out about 1/2 the fluid from the dipstick tube. You can space out the extractions over a few weeks because it is so easy to set up the shop vac and Flo N Go jug.



This works, but on the Honda's with the drain plug that has the magnetic end you want to remove that drain plug to get that grey goop off the magnet.
 
10 miles will be enough. Even just going around the block is sufficient
smile.gif


Originally Posted by lukejo
Ah, I see.
Well, it's a 2012 4cyl Accord with 105,000 miles.
Shifts perfectly. We've not owned that long. Previous owner maintained the car well and claims the ATF was serviced "regularly".
The ATF doesn't smell burnt, but sure is dark...much darker than our Toyota's get after 40-50k miles. Anyway, being an Accord, I prefer the d&f route to a flush.


In that case, you really only need to do one drain
 
Originally Posted by slacktide_bitog
10 miles will be enough. Even just going around the block is sufficient
smile.gif


Correct, to play it safe I'd go around a block that lets it hit all forward gears at least once. lol Then back it up the driveway so reverse gets a workout.
 
^^^ The key is to exercise all the functions of the transmission. Literally "around the block" may not get you to top gear, but a quick spin to your nearest 55+ mph highway will do it.

Since you're talking about a Honda, the official shop service procedure (for multiple D+F) does specify running it through all gears while on the lift, including TC lock-up, and reverse.
 
It's pretty wasteful to do multiple drain&fills in a short time. Either exchange a lot of fluid through the cooler line, or space out the drain&fills to 10-15k miles.
 
Originally Posted by lukejo
I will be doing multiple (4) ATF drain and fills on a car with dark fluid.
How long does it really need to be driven between each d&f to be fully mixed?
200 miles.

10 miles are definitely futile.
 
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