BlackWorks, normally I take what you post as gospel, however my own experience differs. Several techs at my local Toyota dealer actually talked me out of doing a drain and fill as they stated that draining just a few quarts and refilling only mixes the old and new fluids and doesn't provide any benefit except a lighter wallet. We wouldn't drain half our oil and leave half of the used oil in to form a mix of old/new. We also don't mix brake fluid old and new and we don't only replace some of the power steering fluid. Why are we ok with draining an 1/8th of the trans fluid at non-required or recommended intervals.
I see your point that you don't believe that fluid can be "lifetime," and I tend to agree with you, however we should be advocating a non-pressurized flush of the entire system rather than just changing out part of the fluid. I'm not trying to contradict myself from my earlier post, but I believe partial fluid changes are a waste of money.
You know, I have to agree with you there; I only mentioned a single drain and fill based on what our dealership does as practice and what Toyota recommends us to do in the event the fluid needs to be serviced. Which is something I hear a lot of dealerships doing. But I also want to note that I do tend to use the term "Drain and Fill" and "Flush" to indicate flushing the system multiple times with many quarts of fluid and not just one drain and fill procedure, much like we did with older dipstick transmissions. I can see where confusion can arise from playing with terms like that; sometimes I forget people can't read my mind.
On my personal vehicle I did about 3-4 drain and fills with 12 quarts or so to make a nice clean flush. A fluid exchange machine that uses the transmission's own pressure to swap fluid out will not hurt the transmission, but you will still need to check the level afterwards.
I have no problem siding with you on that point. I would much rather a customer do a full flush in some manner, be it repeated drain and fills with 12+ quarts, or a fluid exchange. Toyota does not want us using any machines on WS Transmissions (even though we've established a fluid exchanger will cause no damage), so getting a dealership to do more than drain and fills will be difficult.
True. Your fluid will not be as "clean" as new fluid. But, just because a fluid is darker colored does not mean it is at the end of it's life. Oils are designed to suspend dirt particles within them, hence the darker color. I won't argue that new fluid is not better than older fluid, but the color is not always a good indicator of the "condition" of the fluid.
The issue is that they [Toyota/other manufacturers] are saying that the single hardest working fluid in the entire vehicle is "lifetime." Unless there's been a miraculous breakthrough in lubrication technology that I am unaware of, there is no logical way that ATF can survive the "lifetime" of the vehicle when we have members pushing 400k on their 4th gens. Not to mention Engine Oil technology is barely able to break the 20k Service interval with even the highest end synthetics and filter mediums.
ATF performs the following:
-Lubricant
-Coolant
-Hydraulic Fluid
-Friction Modifier (both to enhance grip and reduce it, paradoxically)
-Cleaner (with detergents and providing a medium to transport suspended particulates of clutch material and clutch plate metallic particles)
There isn't a fluid in the vehicle that is this heavily worked, engine oil is a close second in today's modern VVTi engines. You can't in any sense expect that fluid to hold up under that type of abuse for the "lifetime of the vehicle."
Toyota even backhandedly states it isn't a lifetime fluid by using "severe" driving conditions as a reason the fluid needs to be replaced at 60k and then followed with 30k service intervals.
They also provide no chemical make-up of the fluid to properly analyze (many suspect it is a thinner/heavy additive laden Dexron VI ATF), there isn't even a way for us at the dealer to test the fluid. Most of the "determination" is based on mileage and fluid color, with much of the 100k "recommended service" mileage many dealerships use being due to shuddering and shift issues that seem to be resolved with transmission fluid services around and above those mileages. There also isn't any real evidence to support their "lifetime" claim; even as far as a specific mileage as what constitutes "lifetime" (at least I have not found anything written by them or any other manufacturer that uses "lifetime ATF.") The reality is that this whole sealed transmission and "lifetime ATF" stuff was created out of owners consistently putting the wrong ATF in their vehicles and creating issues in previous generations of vehicles. The manufacturers eliminated that and increased the dependency of the owner on the dealership at the same time by switching to these types of transmissions; another benefit is that many owners will believe "lifetime" and at around 150-200k (the Toyotas among other brands seem to last longer) when that fluid is just useless and starts to degrade the transmission to the point it fails they'll just get a new car because it will be easier.
I realize that sounds rather conspiratorial, but the reality is that many people would rather buy a 200K Corolla or Camry that gets the same mileage as a '14 Corolla for a fraction of the price. Automotive Manufacturers are in the business of selling cars and they can't make them too reliable otherwise people end up buying older models vs. their over-priced, reduced content stuff (*cough* 5th Gen *cough*)
-Post Note-
I have heard from a few industry fellows in the fluids business that ATF is actually designed to blacken when its gone beyond a certain temperature threshold (not because its actually burning up as a fuel) to indicate that it has been stressed too much. I haven't every actually gone and double checked this, but I heard the same thing second hand that was mentioned to other Toyota Technicians. Another interesting tall tale I have yet to verify is that WS ATF turns dark purple after prolonged exposure to oxygen to indicate leaks (which makes no sense to me), I have never verified this and it sounds like more mis-information trickled through backhanded channels; supposedly Toyota Factory Reps (and these guys are supposed to know more than us... supposedly...)
