Rating and using whatever?

[Lola]

This is a simple question (I think), but I don't know the answer !

I have a Toyota Tacoma V6 4X4 AUTO.,
Toyota says the oil should be 5w30, Brakes DOT III, gear lube 75W-90, Differential SAE 90, transmission Dexron III.
Would I be hurting/helping the specifications by going to higher/different ratings, such as DOT 4 on brakes, 0W-40 on oil, gear lube 75W-90 for both, Dexron IV on trans ?
I guess what I am trying to say is do higher lube specifications help or hinder?
Lola

 

[benjamming]

Stay with DOT-3 on the brake fluid. This is one place that going with a "higher" specification is not better i.e. DOT-5 is not "better" than DOT-3. It has more to do with the base formulation of the brake fluid than an upgrade to a specification.

 

[moribundman]

Many brake fluids have are double-rated DOT 3 and DOT 4, with DOT 4 being the newer and tougher spec (Higher dry/wet boiling point). DOT 5 silicone brake fluid is not compatible with any other type brake fluid! However DOT 5.1 is conventional, as far as I know.

 

[unDummy]

You need to understand the specs before deciding if higher is better.

GL-5 in many transmission can't replace GL-4.

I would never use dot5 brake fluid to replace dot3 or dot4. But, I'd use dot5.1 to replace dot4 or dot3 anytime.

Dexron has been upgraded and the new spec is dexronIII-h. But, there are better ATFs.

Oil choice is yours. As mileage builds up, thicker oil might smooth out or quiet down an engine. Trial and error is the norm.

 

[Lola]

Did I mess up? The brake light was coming on so I checked and the fluid was low, so I bought a bottle of Prestone DOT 4 and brought it back up to almost full, about a third of the bottle. The light went off and never came back on till the other night when the temperature here in Maryland dropped into the single digits (7 F). Then the brake light came on until everything was warmed up, and then went off. Still a little low on fluid, should I use the DOT 4, or just get another bottle of DOT 3 and top it off?
Lola

 

[unDummy]

No, you didn't mess up. Dot3 and 4 mix perfectly. Stick with the dot 4.

Why are you losing brake fluid is the real question?