Does ATF go bad with time irrespective of milage?

[Samik8377]

Hello all,

We usually follow a milage based ATF maintenance routine, typically DF. However, does the ATF go bad with time even if the car is used sparingly?

ATFs contain additives alongside the base oil. Can the additives or the base oil lose its effectiveness just sitting there in the tranny of a car which is used for occasional short trips in about 10 years or so?

I am curious about this since all other fluids of a car are supposed to be changed based on miles accumulated OR time (usually specified in years). However, I have never seen any time-based ATF replacement discussion on this forum. Also "few" car makers suggest a time-based ATF change schedule in the user manual and a few others do not.

What are your thoughts on this?

 

[Passport1]

I don't know but your first post is a home run.

 

[xgmad]

No, ATF does not absorb moisture, so there is a very low chance even from the transmission vent for there to be a moisture intrusion unless coolant or something got into the transmission somehow.

ATF wears down with usage, motor oil is different because it is exposed to a more harsh operating environment that is exposed to carbon, fuel, and more heat than a transmission makes.

 

[SureshR]

No, ATF does not absorb moisture, so there is a very low chance even from the transmission vent for there to be a moisture intrusion unless coolant or something got into the transmission somehow.

ATF wears down with usage, motor oil is different because it is exposed to a more harsh operating environment that is exposed to carbon, fuel, and more heat than a transmission makes.

Color change isn’t an indicator either. You will see it turn dirty black in a few thousand miles but ford, for example even has a bulletin out saying this is normal, don’t use it as an indicator that it must be changed.

 

[xgmad]

Color change isn’t an indicator either. You will see it turn dirty black in a few thousand miles but ford, for example even has a bulletin out saying this is normal, don’t use it as an indicator that it must be changed.

Yes this is true, the best way to determine intervals is by using recommended ATF intervals, fluid analysis, or the average of 40,000 to 50,000 miles as is the rule of thumb for light duty usage (For Dexron VI).

 

[weasley]

Theoretically? Yes, it can 'go off' over time. Realistically? No, not in the timescales you will be facing.

Oil oxidises in use and various reaction products are created which propagate and continue the oxidation process. This chain reaction can continue in an unused machine (whether it be an engine, transmission or whatever) however the speed of this reaction is driven by temperature - at ambient temperatures the speed is so glacial as to be irrelevant. However some old barn finds can show the results of this 'stewing' process when the oil pan is removed.

 

[Marcozi]

Some car manufacturers (yes, you BMW) used to tout "lifetime fluids." As the techs would say, "Yeah, that transmission blew up at 124,233 miles but that factory ATF was still good!" My rule of thumb, change the ATF and the filter every 50k miles, and do an ATF exchange (not a flush!!) every 100k miles.

 

[Samik8377]

Yes this is true, the best way to determine intervals is by using recommended ATF intervals, fluid analysis, or the average of 40,000 to 50,000 miles as is the rule of thumb for light duty usage (For Dexron VI).

The reason I asked the question is because of the fact that recommended ATF intervals different from manufacturer to manufacturer, even though their cars are using the same transmission and same spec ATF ! Some even say that ATF change is never required!

Does the average of 40,000 to 50,000 miles as the rule of thumb for light duty usage apply for older ATFs like JWS3309 or DEXRON 3 too?

Some car manufacturers (yes, you BMW) used to tout "lifetime fluids." As the techs would say, "Yeah, that transmission blew up at 124,233 miles but that factory ATF was still good!" My rule of thumb, change the ATF and the filter every 50k miles, and do an ATF exchange (not a flush!!) every 100k miles.

So theoretically if you take 15 years to reach 50K miles, would you still use the same ATF for 15 years? (Provided the gears shift smoothly, the ATF is not too dark, and transmission does not overheat during your usage)

 

[Marcozi]

The reason I asked the question is because of the fact that recommended ATF intervals different from manufacturer to manufacturer, even though their cars are using the same transmission and same spec ATF ! Some even say that ATF change is never required!

Does the average of 40,000 to 50,000 miles as the rule of thumb for light duty usage apply for older ATFs like JWS3309 or DEXRON 3 too?



So theoretically if you take 15 years to reach 50K miles, would you still use the same ATF for 15 years? (Provided the gears shift smoothly, the ATF is not too dark, and transmission does not overheat during your usage)

Great question. One thing you would have to know is how the is driven. If it's utzing around town you're likely ok. But if you se the car to tow a trailer or you take it the drag strip, then I'd change every 5 years or so. Let me caveat that. I've never owned a car with an automatic transmission. My car have been manuals.

 

[Samik8377]

No, ATF does not absorb moisture, so there is a very low chance even from the transmission vent for there to be a moisture intrusion unless coolant or something got into the transmission somehow.

ATF wears down with usage.

Based on the responses here I think it boils down to how long(in terms of years) the additives in the mix (friction modifiers, anti foaming agents etc) last to a satisfactory level of performance.

Another way of looking at this is: if an OPEN ATF bottle is stored, for how many years it stays good.

Keeping high temperature driven oxidation outside the scope of discussion here, since oxidation and resultant degradation of the oil itself is visible through darkening of the ATF color.

 

[weasley]

Another way of looking at this is: if an OPEN ATF bottle is stored, for how many years it stays good.

It depends on a number of factors:

• exposure to UV
• humidity
• ambient temperature
  • absolute
  • variability

I'd guess it'll stay in shape for many years so long as it is kept well and protected from contamination.

 

[xgmad]

It depends on a number of factors:

• exposure to UV
• humidity
• ambient temperature
  • absolute
  • variability

I'd guess it'll stay in shape for many years so long as it is kept well and protected from contamination.

If kept in a dark place, it should last longer than all of us. I don't think humidity is an issue with ambient temperatures since oil does not really absorb moisture.

 

[John105]

Color change isn’t an indicator either. You will see it turn dirty black in a few thousand miles but ford, for example even has a bulletin out saying this is normal, don’t use it as an indicator that it must be changed.

My Lexus at 86k where indie assured me 100% safe to drain/fill…black. On 3rd drain/fill, still black coming out. My GM diy after 2 drain and fills, pink. I decided I would not obsess over the colors….

 

[weasley]

If kept in a dark place, it should last longer than all of us. I don't think humidity is an issue with ambient temperatures since oil does not really absorb moisture.

You're generally right, although there is always a little bit of water held up in the oil, especially if there are detergents in there which can hang on to water.