dot 3 or dot 4

[scubasteve]

Might seem like a silly question but I know in all the manuals ive seen the gq tb42s calls for dot3 fluid for the clutch. My question is, is it ok to use dot 4 as its suppose to be a better product for newer cars or should I stick to dot 3 only for the clutch?

[nissannewby]

Dot 3 mate across the board (Brake and clutch) keeps top ups and changes easy.

[mudski]

Dot 4 can be used in replace of DOT3. The major difference between the two is the boiling point. DOT4 is slightly higher, but only by about six degrees though. I use DOT4 because I see no point in using two different brake fluids on two cars I have. But you can use DOT4 over DOT3, just make your you flush the old fluid out. Which you should do anyway when flushing or changing fluids.

[nissannewby]

Dot 4 can be used in replace of DOT3. The major difference between the two is the boiling point. DOT4 is slightly higher, but only by about six degrees though. I use DOT4 because I see no point in using two different brake fluids on two cars I have. But you can use DOT4 over DOT3, just make your you flush the old fluid out. Which you should do anyway when flushing or changing fluids.

While I haven't experienced it I have read of people having issues with seals in the braking system from the slightly different properties in the dot 4 to give it the higher boiling point. Now whether this was a maintenance thing as you touched on mudski and the old fluid was mixed or poor brake system maintenance in general who knows. I used to to put it in my GQ and never had an issue but like my experience with the gearbox oil (API-GL4 as specified by Nissan) my thinking is if its specified why use something else. However I will agree that if you want to use dot 4 and do not know exactly what is already in then a system flush is a very good idea. Also date your bottles once you open them as brake fluid is hydroscopic (it absorbs water) and after a while can be no good to use.

[Alitis007]

While I haven't experienced it I have read of people having issues with seals in the braking system from the slightly different properties in the dot 4 to give it the higher boiling point. Now whether this was a maintenance thing as you touched on mudski and the old fluid was mixed or poor brake system maintenance in general who knows. I used to to put it in my GQ and never had an issue but like my experience with the gearbox oil (API-GL4 as specified by Nissan) my thinking is if its specified why use something else. However I will agree that if you want to use dot 4 and do not know exactly what is already in then a system flush is a very good idea. Also date your bottles once you open them as brake fluid is hydroscopic (it absorbs water) and after a while can be no good to use. Your spot on the money there Matty about the different properties that increase the boiling point of DOT4 fluid, they attack the rubber in wheel and slave cylinders that are used in cars made to suit DOT3. I personally have seen them fail within a month of using the wrong fluid after replacement and flushing of the system. Using DOT4 on a DOT3 braking system with disc brakes is not obvious in the short term it is still doing damage to the seals on the brake caliper pistons in the long run.

You can use super DOT4 to replace DOT4 but not DOT 5 and not DOT4 to replace DOT3, if that makes sense

Edit: i forgot to add that only Super DOT4 can also be used on DOT 3 and DOT 5 Disc brake braking systems BUT NOT DRUM BRAKING SYSTEMS OR CLUTCH HYDRAULIC SYSTEMS

[scubasteve]

Cheers for clearing it up guys sounds like dot 3 all round for me. Will make the maintanance super simple and safe guards against and seals going. Quality technical info guys thanks