DOT3 vs DOT4 brake fluid?

I'm planning on flushing out the brake/clutch lines on the 350Z in the next week or two. And I'd obviously like to put something in a bit more performance oriented.

The Owner's manual calls for DOT 3 fluid. It's my understanding that the chemical makeup between the fluids is different enough that some systems might not tolerate the other.

So does anyone know for certain if DOT4 brake fluid is safe to use in the 350Z? This obviously a warranty concern. If I used the non-recommended fluid and had the seals disentigrate, that would be on me. And I shudder at the thought of what the ABS unit costs.

DOT3 and DOT4 are both polyglycol based. You're fine to use DOT4 in your car.

93celicaGT2 is correct. DOT4 is a similar formulation to DOT3, just has a higher boiling point. It's DOT5 you want to run away screaming from. I've mixed DOT3 and DOT4 for years with no real problems.

ues Valvoline DOT 3 and 4 Synthetic Brake Fluid (32 oz.) works grate and has a grate price.

SlickDizzy wrote: 93celicaGT2 is correct. DOT4 is a similar formulation to DOT3, just has a higher boiling point. It's DOT5 you want to run away screaming from. I've mixed DOT3 and DOT4 for years with no real problems.

Yeah, DOT5 is different formula. DOT5.1 can be used in DOT3/4 systems.

I use DOT 4 in everything I own, and that spans about 5 decades worth of cars. Its completely compatible with DOT 3, and has a higher BP. Good stuff. The Valvoline DOT 4 synthetic is my choice, the BP is actually not significantly less than many "racing" brake fluids that cost 4X more.

Run away from DOT 5. Do not use, do not pass go, do not collect $200.

I use the Valvoline DoT 4 synthetic when I can find it in all my vehicles calling for DoT 3. I think Autozone is carrying it again.

DoT 5 rocks. All systems that I take all the way down are going back together with DoT 5. I didn't so much as check my MC level for maybe 15 years on my bike. DoT 5. Pulled the system open fully expecting it to be totally junk and there wasn't a spec of corrosion, just some very minor wear.

Dr. Hess wrote: DoT 5 rocks. All systems that I take all the way down are going back together with DoT 5. I didn't so much as check my MC level for maybe 15 years on my bike. DoT 5. Pulled the system open fully expecting it to be totally junk and there wasn't a spec of corrosion, just some very minor wear.

I'm glad I'm not the only one who thinks that.

yes, they can't be mixed. And if you are not careful, there could be air.

But there's NO water. I ran it on my Alfa for many years after I complete rebuild, and cleaning of the system. It was awesome.

AND it has a very high boiling point- never really had over heating problems on the track.

BTW- to the OP- why do you want to change to DOT4? Is there some return on the change you expect to be that wonderful? I wonder that a lot- people spend a lot of money doing some conversion to not really see any significant beneift. Just re-did the brakes on my Miata, and got trusty NAPA DOT3. Didn't see any real point to change it.

E-

If you're generating some heat in your brake system with hard use, DOT4 is cheap insurance. It's not an expensive change, if you budget $15 you're probably going to have some money left over.

It's mainly if I'm going to run a heavy pig like a 350Z at Hallett for an occasional HPDE a more performance oriented brake fluid seems in order. I wasn't expecting that DOT4 will never boil or absorb water or never need to be changed again or any other "wonderful" unknown attribute.

93celica, I'm aware they are both glycol based, but it is my understanding (correct me if I'm wrong) that the DOT4 contains borate esters that DOT3 does not. And that not all systems tolerate the slightly altered chemistry. Given that there is a possibility, regardless of how unlikely, I still like to know for sure.

Hence the question.

There are DoT 3's that not all systems tolerate. I run the DoT 4 in my Esprit at Hallett, and if a 21 year old English system can tolerate it, your 350Z won't know the difference, except for the higher boiling point, handy when heading into The Bitch at 95-100.

I've only been a passenger on HPDE's riding clockwise and The Bitch is a bit nerve racking until you realize just how late the car can brake!

Or into Turn 1 at ????????? running counter-clockwise.

I know on the R6, depending on how good I got out of 10, the braking zone into Turn 1 was around 125.

On my buell there was a warning in the manual that some of the older bikes used crush washers on the banjo bolts to the brake caliper that aren't compatible with DOT4 and if you do change the fluid to DOT4 you want to replace the crush washers. It was either shiny or black washers that weren't compatible, I could check. This was on my bike though so maybe cars are different.