To change or not to change ATF fluid 3.0 x5

[Acidphase]

Originally Posted by JCL

I disagree that fluid colour means very much. We have to separate engine oil and transmission fluid here, because they can be dyed different colours, but it is a myth that colour relates to fluid quality. A good fluid can be dark, and a clear fluid can be worn.

If a transmission fluid is burnt, that is a sign that it has been overheated. That isn't based on colour, but smell. If a fluid is milky, that is a sign that it has water in it. That colour matters.

But to suggest that it should have a red colour is wrong, because only some transmission fluids are dyed red. More often amber these days.

Transmission fluids are designed to keep particles in suspension (particles too small to be filtered out). That property will make them non-translucent. That doesn't mean they are worn out, it means they are functioning as designed.

Using engine oil as a different example of the limits of colour analysis, a diesel will soot up the oil in minutes, and it will look black. Some will get very worried and claim that their shop must not have changed it, given the colour, but it is perfectly normal for it to be black.

Anyone using a colour chart to sell oil or fluid changes is overselling, IMO.

I never said they "Had" to be red. Listen I'm not going tit for tat it's not worth it believe what you want you're entitled. Comparing diesel fuel applications with synthetic mineral oil applications that never sees combustion is a new one but okay lol
If your transmission fluid is turning brown and black this isn't good plain and simple regardless of what color it was lol
I really don't feel like getting into a molecular level on this one with carbon and oxidation so whatever you reply with next I'll just agree it's easier these days..
~Locomotive Engineer

[JCL]

Originally Posted by Acidphase

I never said they "Had" to be red. Listen I'm not going tit for tat it's not worth it believe what you want you're entitled. Comparing diesel fuel applications with synthetic mineral oil applications that never sees combustion is a new one but okay lol
If your transmission fluid is turning brown and black this isn't good plain and simple regardless of what color it was lol
I really don't feel like getting into a molecular level on this one with carbon and oxidation so whatever you reply with next I'll just agree it's easier these days..
~Locomotive Engineer

I agree you didn't say they had to be red. But there are a lot of posters on here who aren't engineers, and a chart that shows amber fluid with a label that says change it now may not be helpful.

My only real point was that colour is generally a poor indicator of anything with a lubricating fluid, unless it shows water.

And the issue with transmission fluid is that it isn't really designed to be much of a lubricant. It is a hydraulic fluid that carries heat, and has specific frictional characteristics at the point of clutch lock up, but the lubricating demands on it are very minimal, particularly with modern transmission control strategies.

I am a firm believer in preventative maintenance, lots of history with mining and industrial equipment. I do regular PM work on my BMWs. What I don't promote personally is changing out things for the sake of changing them out. Preventative maintenance should be designed to avoid catastrophic failure, to maintain the function of a component, and to manage TCO over the machine's life, IMO. If it doesn't contribute to those things, it is maintenance, and it adds to cost, but it is hard to call it PM.