Multiple AT drain and refill a waste of money.

Status
Not open for further replies.
Joined
Apr 29, 2017
Messages
126
Location
Orange County CA
In researching about how to service my own transmission on my 2002 Toyota Sienna I naturally came across the drain and refill method. And what I noticed from some of the post was that people would drain their transmission then fill it then drive it for x amount of time and drain and refill again and they may do this two or three or four times. Obviously the idea being to get as much fresh tranny fluid in there as possible. But what I haven't heard anybody point out, maybe because it's so obvious that it's not necessary, then again maybe it's not so obvious, is the waste of good transmission fluid using this method. Let me just give an example to show what I mean. For the sake of argument let's say your transmission holds 4 quarts. So you drain out 1 quart and then you put in 1 quarter of fresh. Your transmission fluid now has 25% fresh fluid in it. Now you drive your car around for a couple of days to mix up the old with the new fluid and then you drain off another quart. Unfortunately you're not just draining off old transmission fluid now. 25% of that fluid you are draining off is the new fluid you put in there. So when you add your new quart back in you're not adding a full quart of new fluid to the old, for now a total of 2 new quarts in your system, you are replacing that 25% of of a quart of the new fluid you just drained. And now only 75% of that from quart is new fluid in your system. Therefore your transmission does not have 2 new quarts in it for 50% new in this 4 quart system after this second drain and fill, it has 1.75 new quarts. And I think that give you 37% new. Then you repeat the procedure for a third time and now you're draining off yet more new (37%) transmission fluid from the last two days procedures and the one quart you now put in has to replace that 37% and then the 63% that is old. And it goes on and on like that to where each time the precent of the new transmission oil you are draining out, and throwing away, is a greater and greater percentage. My own car holds about 8 quarts total. The math I did for it told me that if I wanted to achieve a 75% freshness rate of my transmission fluid using the multiple drain and refill method, assuming I did 2 quarts at a time, I would have to do that 10 times. In other words I would have to use about 20 quarts to get 6 quarts worth freshness in the system. And I use 2 quarts for my example because the suction pump I got is only able to get out 2 quarts at a time. But the math carries out, Each time you drain and refill you're taking out X% of the fresh fluid you put in from the prior procedure(s). And drain and refill once every 30000 miles? That means that at 30,000 miles X percent of your fluid will be fresh and x percent have 30,000 miles on it. Then you do that again at 60,000 miles you have X percent that is fresh, X percent with 30,000 miles on it and X percent with 60,000 miles on it and so on and so forth. That all doesn't sound good to me. Of course a lot of this falls under the better than nothing category, especially if you do not have the luxury of owning the car from new and starting a proper service schedule and method. And then it seems that draining as much as you can in one sitting is the better way to go. Like from the cooling lines. Ok. Just putting this out there as a bit of consciousness raising. If my theory is wrong please tell me. I would very much like it to be.
 
Last edited:
Joined
Aug 14, 2010
Messages
12,968
Location
Northern Kentucky
You have it about right. It does waste some fluid but that's a small sacrifice to get more old fluid out. If stay on top of a vehicle from new you can just drain and fill every 30k.
 

4WD

$50 site donor 2023
Joined
Sep 21, 2010
Messages
20,173
Location
Texas via IAH
Not wrong - on my Canyon I'm set up to drain 4 quarts and change a spin on remote filter in 20 minutes - so I do that once a year and 1/3 of the fluid is new and filtered well. I'm always on the lookout for deals on Dex VI. (And the $3 each Bosch Distance Plus oil filters I just grabbed are that size)
 
Joined
Dec 18, 2016
Messages
797
Location
Indiana
I changed the fluid 3 times on a scion xb with 100k and original Transmission fluid. The fluid went from a slightly brown color to nice fresh looking red. I see your point, but the fluid looked much better after the 3rd change than the first. It's kind of like your fuel tank, how long does some of the original fuel stay in there?
 
Last edited:

JHZR2

Staff member
Joined
Dec 14, 2002
Messages
49,015
Location
New Jersey
OP, I'd say you're spot on. My concept is somewhat different.... Do the drain and fill, but not as often. Do a drain and refill maybe every 10k or so, in order to keep the fluid fresher. That way by the time you do it again, even the 25% you just swapped a while ago will have aged a bit... I like the idea of freshening a transmission... But even old school transmissions and fluids only needed service every 3/36 or so... Newer transmissions may not need any... But keeping the overall life a little newer does help...
 
Joined
Aug 15, 2008
Messages
4,963
The cooler line exchange method is much better, but can carry more risk like fluid starvation (possible but not likely) and leaks (from disconnecting line fittings). If you do the drain and fill method early on in a car's life, and do it once every few years, then think of it as replenishing the additives more than trying to get 100% clean fluid again.
 

4WD

$50 site donor 2023
Joined
Sep 21, 2010
Messages
20,173
Location
Texas via IAH
That's close to what I'm doing. Used to fight the messy pan and 'rock catcher' filter every 30k - but now with drain plug and remote filter I'm doing 1/3 change every 10k - clean & easy and better filtration ... (Added a cooler during filter installation too)
 
Joined
Jun 23, 2014
Messages
3,236
Location
Phoenix, Arizona - USA
Originally Posted By: MichaelRS
And drain and refill once every 30000 miles? That means that at 30,000 miles X percent of your fluid will be fresh and x percent have 30,000 miles on it. Then you do that again at 60,000 miles you have X percent that is fresh, X percent with 30,000 miles on it and X percent with 60,000 miles on it and so on and so forth. That all doesn't sound good to me.
This is pretty much what I do in my 2010 Fusion, which has the 6F35 trans, known to be hard on fluid and a bit finicky. Ford techs recommend a multiple drain&fill every 30,000 miles. I am now using the following regimen: Approximately every 30,000 miles: - I pull the drain plug on the trans and let it drain completely once - This gets me about 4.5 quarts of fluid out. I then put the drain plug back in and fill it once with a gallon of new fluid, and verify on the stick that it's within the hashes. Then I drive it around the block a few times to warm it up a bit, and with it running, add more fluid until it's 'near' the full mark.. it will expand just a bit when full hot. - I then take the drained fluid and send a sample into the lab for a UOA. If the results indicate a somewhat high level of wear metals and/or contaminants, I'll either reduce my next drain&fill time frame (say 25,000 miles instead of 30,000), or I'll do another drain&fill the next weekend (or day off). This way, I let the trans fluid tell me if it needs a 2nd drain&fill, or if I can leave the partial fill in. Based on my latest UOA, it seems that doing a single drain&fill at 30,000 miles works decently well, and since I did my last one at 24,000 miles along with an oil change, I'll be able to see how much of a difference shortening the interval helps, and I can adjust accordingly. For what it's worth - the car will be hitting 230,000 miles tomorrow during my daily work commute, and it still has the original trans, so I'd say the 30,000 mile single D&F regimen works well enough.
 

MichaelRS

Thread starter
Joined
Apr 29, 2017
Messages
126
Location
Orange County CA
Thanks for your input everyone. Now let me ask you about ATF color. I just did my 3rd suck it out through the dipstick and refill. And I did 2 quarts at a time, with about 150 between times 2 & 3, because that's all my pump can get. In the clear plastic jug I use, to measure what I pulled out, the overall appearance of the ATF is a dark brown and I can't see a bit of light through it. But when I slosh it around a little on the sides as it runs down it's more the reddish color. Also when I do the blot test on a white paper towel it looks fairly pink-red. But the fact the bulk of it looks so brown and dirty in the jug concerns me. The original owner, at least according to Carfax and a dealer report, did a transmission FLUSH at 30 and 50 thousand miles. There is no record of any other Transmission Service until I got the car at 136k, at which point I had my mechanic drain, drop the pan and replace the filter and obviously whatever transmission fluid came out by that method. Then I forgot about it till now 41k miles later at 177,6xx. So, based on all that, is the fluid in their VERY bad, or is that how most fluid would look anyway if you had been going a long doing 30 or 40 thousand mile drains and refills on it?
 
Joined
Jun 23, 2014
Messages
3,236
Location
Phoenix, Arizona - USA
Perhaps not the best picture, but here's from my latest drain (with ~24,000 miles on it): It's kind of purple-y red.. and doesn't let much light through. Previous drain was on a 30,000 mile interval, and was a single drain&fill.. so this fluid was a mix of fresh and older fluid. Each drain&fill gets about 50% of the fluid out on this trans.
 

MichaelRS

Thread starter
Joined
Apr 29, 2017
Messages
126
Location
Orange County CA
Okay. Don't know why link is not copying. But it was pretty good information on four stages of automatic transmission fluid with pretty clear pictures of examples. So I guess I'm doing okay. My goal is to try to reach 200,000 before I get in there and drop the pan and change the filter and do a more complete fluid exchange thru the cooler lines.
 
Joined
Sep 30, 2013
Messages
15,064
Location
Indiana
Would a cooler line flush replace more old fluid with less? Does your van have a serviceable filter? If it makes you feel any better, I did a cooler line flush last year on the Volvo in my signature with about 14 quarts. ~150k on the original fluid. It has an Asin Warner transmission and I am assuming takes the same fluid your Toyota does. You should be fine since your vans fluid has been changed throughout the years.
 
Last edited:

JC1

Joined
Nov 29, 2008
Messages
6,735
Location
Oshawa, Ontario Canada
Originally Posted By: MichaelRS
Thanks for your input everyone. Now let me ask you about ATF color. I just did my 3rd suck it out through the dipstick and refill. And I did 2 quarts at a time, with about 150 between times 2 & 3, because that's all my pump can get. In the clear plastic jug I use, to measure what I pulled out, the overall appearance of the ATF is a dark brown and I can't see a bit of light through it. But when I slosh it around a little on the sides as it runs down it's more the reddish color. Also when I do the blot test on a white paper towel it looks fairly pink-red. But the fact the bulk of it looks so brown and dirty in the jug concerns me. The original owner, at least according to Carfax and a dealer report, did a transmission FLUSH at 30 and 50 thousand miles. There is no record of any other Transmission Service until I got the car at 136k, at which point I had my mechanic drain, drop the pan and replace the filter and obviously whatever transmission fluid came out by that method. Then I forgot about it till now 41k miles later at 177,6xx. So, based on all that, is the fluid in their VERY bad, or is that how most fluid would look anyway if you had been going a long doing 30 or 40 thousand mile drains and refills on it?
Have you ever dropped the pan and replaced the filter on the van? I had a 98 sienna and I dropped the pan three times and changed the filter. You wanna get that goop off the bottom of the pan. By doing that the fluid was always a nice red. I would only do drain and fills on that van. Started used Mobil 1 ATF, but then switched to Maxlife.
 
Joined
Oct 7, 2012
Messages
931
Location
North Carolina
For the OP, here is the transmission drain/refill replacement ratio for his example of replacing 1 qt. in a 4 qt. unit: #1 25.00% #2 43.75% #3 57.81% #4 68.36% #5 76.27% #6 82.20% #7 86.65% #8 89.99% #9 92.49% 10 94.37%
 
Joined
Aug 19, 2010
Messages
10,676
Location
Champlain/Hudson Valley
I agree. But do a drain & fill first THEN go straight into your cooling line pump-out. This way the transmission will be sucking up nothing but clean fluid. You won't be adding clean fluid to a half emptied sump. EXAMPLE: Pump outs usually recommend pumping out 2 quarts-shut off engine-replace the 2 quarts-restart engine and pump out 2 more-shut off engine-replace the 2 quarts etc. This is recommended so you don't suck ait into the system. In my case the sump holds 4 quarts. I'd be pumping out 2 and adding 2 new quarts to dirty fluid. Starting with a fresh sump makes it a more efficient process. The argument against wrestling with stuck cooling line fittings wasn't mentioned. If things are super crusty and old, a succession of less efficient drain & fills can make sense.
 
Joined
Feb 27, 2006
Messages
3,462
Location
Cincinnati
ATF is cheap compared to transmission work. I do drain and fills every two years on both my Honda's, usually about 15k. 3.5 and 4 quarts respectively. Still going strong at 243k and 91k.
 
Joined
Jun 15, 2003
Messages
38,370
Location
ME
Your math is right but is also accounted for by the engineers. If they say do a drain and fill every X, they are accounting for the leftovers. This is why you'll occasionally see instructions to run to 100k then do something every 50k. Radiator drain and fills are the same situation, about half new fluid. People try to out-think this and change "all" the fluid, when it was decided that "half" would bring enough newness to the scene. Then of course there's the theory that bean counters outrank the engineers, and stuff isn't designed to last forever. We don't know until 15 years and 200k have passed, and the present powertrain hasn't proven itself over the last 15 years, so a new glitch may be lurking that is avoided by over-maintaining. I don't like cutting tranny cooler lines, which adds a failure point, and I don't like fighting engine block drains. So I change half at a time, as instructed. My stuff rusts out before the systems give out. Good enough for me.
 
Status
Not open for further replies.
Top