I want to change all fluids.. but how many are there?

[Carbon]

For me it first came up at lunch with some automotive engineers I happened to be working with.

But it is good idea... No, it is not on the scheduled maintenance list, just as transmission fluid currently is not.

So who do you trust? Brake fluid - Wikipedia, the free encyclopedia says "Most automotive professionals agree that glycol-based brake fluid, (DOT 3, DOT 4, DOT 5.1) should be flushed, or changed, every 1–2 years." Five years seems reasonable to me.

How about Google for a sampling of recommendations.

[4x4 rav]

Originally Posted by Carbon

For me it first came up at lunch with some automotive engineers I happened to be working with.

But it is good idea... No, it is not on the scheduled maintenance list, just as transmission fluid currently is not.

So who do you trust? Brake fluid - Wikipedia, the free encyclopedia says "Most automotive professionals agree that glycol-based brake fluid, (DOT 3, DOT 4, DOT 5.1) should be flushed, or changed, every 1–2 years." Five years seems reasonable to me.

How about Google for a sampling of recommendations.

Suit yourself!
I'm, however, being exceedingly honest.
An engineer can write equations, using math and physics, to describe a system ( e.g. a motor, braking circuit, etc.). But if you tell that same engineer to leave the classroom and come to a garage to diagnose and solve a problem on a car, he or she wouldn't be able to. But of course, there are exceptions. Many things that look good on paper, don't look so go good in practice.
By the way i received my advice on brake fluid by 2 master technicians. who will you trust? the technicians who years of experience or someone who is trying to "sell you the san francisco bridge" ( someone who has been trained to write equations, but a looser outside of that)?
sncerely.

[pepepeter]

folks dont know what happened, but i am referring to this post:

I want to change all fluids.. but how many are there?

which is concerned with the fluid grade for the rear diff and transfer case...

[Carbon]

Originally Posted by pepepeter

Now, I have to figure out what grades of fluid to put in the rear and transfer case. The 08 specs seem a bit odd, just want to make sure I have the correct fluids for my 08 awd i4 sport. see this: Attachment 2303 it claims transfer case is SAE 85W-90 (>0 F) and rear diff is SAE 90 (>0 F).

THANKS!!!!

API GL−5 grade.

You could use 80W-90 or even 75W-90 synthetic for both.

[vanib]

Manual suggests 80W-90, in case you are still under warranty. No need to get expensive lube if you plan to change it every 2 years.

[pepepeter]

Originally Posted by Carbon

API GL−5 grade.

You could use 80W-90 or even 75W-90 synthetic for both.

Originally Posted by vanib

Manual suggests 80W-90, in case you are still under warranty. No need to get expensive lube if you plan to change it every 2 years.

Thanks!!!

So from both your responses, isnt the 80w-90 intended for temps below 0deg F??? I live in AZ and it will never reach that temp in my lifetime. Is there a concern using this viscosity and weight in temps that top 115F between Jun-Aug??

[Carbon]

Originally Posted by pepepeter

Thanks!!!

So from both your responses, isnt the 80w-90 intended for temps below 0deg F??? I live in AZ and it will never reach that temp in my lifetime. Is there a concern using this viscosity and weight in temps that top 115F between Jun-Aug??

At higher temperatures, they will be each acting as a 90 weight. I don't think that Toyota is saying that the 80W-90 is only for use below 0F, but rather that it should be used if 0F may be encountered. However if you are concerned, you could get straight 90 weight to exactly match the manual.

In the 2009 owner's manual, the fluids for the differential and the transfer case are speced the same way:

Hypoid gear oil API GL-5
Above 0F (-18C): SAE 90
Below 0F (-18C): SAE 80W or SAE 80W-90

You might read this thread Did enyone replace diff and transfer fluids? where using higher viscosity was discussed.

[friendly_jacek]

Originally Posted by Carbon

API GL−5 grade.

You could use 80W-90 or even 75W-90 synthetic for both.

I'm not sure 75W90 is the best advice.
2 reasons.

1. I used 75W90 redline GL5 oil in my Subaru thinking (just like you) that if 80W90 is good, premium 75W90 is better. 20,000 miles later, annoying rear diff noise developed. To be fair, Subaru was very hard on the gears with a lot of metal in oil. I didn't see that in RAV4.

2. the SAE grade specification is based on 100C (212F) temp viscosity. The diff are not going to be that hot, I measured 100-120F external temp in RAV4 IIRC. Thus, 75W90 will be much thinner compared to 80W90 and especially 90 during the working temps. While this could be potentially beneficial in very cold, but not necessarily in hot climate.

Thus, 75W90 is not comparable to 90 in the working temp conditions.

My read is the engineers specified 90 for driving above 0F. Keep in mind that is equivalent to SAE 110 in the revised gear SAE rating. That was "lost in translation" as 80W90 for everyone anytime. Now, even thinner 75W90 are used by owners. This is going away from the original specification.

[pepepeter]

Originally Posted by friendly_jacek

... Keep in mind that is equivalent to SAE 110 in the revised gear SAE rating. That was "lost in translation" as 80W90 for everyone anytime. ..

this is new to me (dont keep up with this type of information). so if the bottle in autozone states SAE 90..it still SAE 90 and not equivalent to some lower weight/viscosity diff fluid, correct? I ask because if SAE 110 (new scale) = SAE 90 (old scale), then is there a SAE 90 (new scale) = ???? (old scale).

Just want to make sure the bottle i get off the bottle is indeed the spec'd bottle by the manual.

[dtalk]

I agree with Carbon for brake fluid flush, most shops say every three years. Why, because brake fluid is hygroscpic (absorbs moisture) and it is also the lubricating fluid for the internals of the brake system.. not to mention the corrosion prevention that is lost as it gets older. You can get by not doing it, but I have seen what happens to cars that have not had this done in a hard braking situation and it is not pretty. Just saying it is up to the owner.