Difference between Super DOT4 and Synthetic DOT4

[Tom Slick]

I went to Wallyworld to get some filters for my truck and some fluid for the clutch in the Z. The owners manual says to use Super DOT4 brake fluid in the clutch reseviour (sp), but all that I could find was Prestone Synthetic DOT4 brake fluid. I went to Auto Zone and Kragen and all they had was the Synthetic DOT4. I went to Chevy and they had the Super stuff, but for 16oz it was $8.00. The Prestone stuff was only $2.98 for 32oz. I'm not cheap, but if I can use the Synthetic stuff in lieu of Super I'll go that route.

Is there a difference other than GM calls their DOT4 fluid Super. Shouldn't all DOT4 fluids be compatible?

[No Doubt]

Chemically speaking, all DOT 4 fluids are all comprised of glycols, glycol ethers and borate esters. DOT 3 fluids lack the borate ester component.

The major difference lies in the required minimum boiling points which must be in accordance with Federal Motor Vehicle Safety Standard (FMVSS) 116...

DOT 3 Dry= 401°F / Wet = 284°F

DOT 4 Dry= 446°F / Wet = 311°F

Super DOT 4 usually indicates it has a dry boiling point which exceeds 500°F. Sometimes these fluids are known or labeled as DOT 5.1.

DOT 5 Dry = 500°F / Wet = 356°F (without the .1) Utilizes Silicone chemistry and is NOT what you want.

The GM Super DOT 4 fluid is chemically compatible with regular DOT 4, but you may lose some boiling point protection with normal DOT 4.

I say "may" because although they call it "Super DOT 4" I don't know the exact boiling point figures and thus it may be a marketing buzzword.

However, you can always use a DOT 4 or DOT 5.1 fluid where the boiling points are known.

[Tom Slick]

So, there won't be any issues if I mix the Super DOT4 with the Synthetic DOT4?

[No Doubt]

As per above, they are chemically compatible.

However, and again per the above, you may lose some boiling point protection depending on the boiling points of each fluid.

Simply put, you're better off with a Super DOT 4 (assuming it's really "Super") or a DOT 5.1.

Note: I can't say for certain whether or not the GM Super DOT 4 Clutch and Brake fluid meets the specs usually reserved for "Super" DOT 4. There is no required specification for a Super DOT 4 fluids minimum boiling points as there is with the other fluids. Thus, one can call their fluid "Super Heavy Duty Supreme DOT 4" or whatever, yet it can have the boiling points of a regular DOT 4 fluid. It's called marketing.

GM likely does use real Super DOT 4 which has higher boiling points. But again, I can't say for certain.

I wish there was a simpler way to explain this, but like many things there is often more to the story than meets the eye.

[Tom Slick]

Thanks for the info.

[ZO6 AL-X]

I decided to go with the Amsoil Series 500 DOT 3 Brake Fluid.

Their fluid has the following:
- Dry Boiling Point of 525* F
- Wet Boiling Point of 313* F

Amsoil recommends this fluid for the C6 Z06 as well as the C5 Z06. Look into it and see how you like it.

AMSOIL - Series 500 High-Performance DOT 3 Brake Fluid (BF3)

[DJWorm]

Just to be perfectly clear:

1. The term "compatable with other fluids" when used to discribe brake and clutch fluids means the fluid CAN be used with another fluid IF the other fluid is also "compatable with other fluids". They BOTH must be compatable.

2. Just because you CAN admix fluids of a different type doesn't mean you should. In fact you SHOULDN'T. Brake and Clutch fluids do not actually mix when put in the same container even when the base is the same chemical composition but different DOT rating.

Therefore if you admix a higher rated DOT fluid with a lower one the resultant fluid will have the original boiling point of the lower grade fluid no matter what the concentration percentage....admixing will NOT average the boiling points.

So if you added a higher rated DOT fluid to a lower rated "compatable" fluid and expected slightly better performance you just wasted your money.
Also the technique of add - bleed - add - bleed - add - bleed - etc. does NOT work either.

In essence what the "compatable with other fluids" means is:

1. If you are NOT concerned about boiling point and do not track the car then you can "top off" the reservoir with different fluids along as they are "compatable"; but don't expect any performance enhancement.

OR

2. If you are concerned with boiling points and are switching to a higher rated DOT fluid you must:

A. With Compatable fluids :
- you need to drain the original fluid
- with new fluid: fill, flush, drain & discard *
- fill with new fluid

B. However with NON-compatable fluids you MUST add an additional step:
- drain original fluid
- with new fluid: fill, flush, drain & discard *
- REPEAT fill, flush, drain & discard with new fluid *
- fill with new fluid

* ALWAYS purge & bleed the ABS with a Tech II Analyser.

[No Doubt]

The original question was "Shouldn't all DOT 4 fluids be compatible?" And the answer is they are.

However, what GM refers to as "Super DOT 4" may or may not have higher boiling points than regular DOT 4 fluids, which are federally mandated to have a minimum dry boiling point of 446°F and a minimum wet boiling point of 311°F.

There is no federal specification for "Super DOT 4", although fluids labeled as such often meet the same minimum requirements specified for DOT 5.1.

All brake fluids must meet federal motor vehicle safety standard # 116. In accordance with this standard, there are three Department of Transportation (DOT) minimum specifications for DOT 3, DOT 4, and DOT 5.1 brake fluids. That is, those fluids with a Polyalkylene Glycol Ether base. As such, all of them are chemically compatible* with one another.

DOT 5 fluids utilize a Silicone base and are NOT compatible with the others. They may also be incompatible with some brake systems.

*Chemical compatibility does not mean they all offer the same boiling point protection, as DJ mentioned. Therefore, to insure reliable braking in situations where high brake temperatures may be encountered, flushing the brake system as outlined is wise.

[DJWorm]

NO.....all DOT 4 fluids are NOT compatable.

AP PRF 660 exceeds DOT 4 and is NOT compatable with any other fluid

AP 600 exceeds DOT 4 and is NOT compatable with any other fluid

AP 550 exceeds DOT 3 but IS compatable with other fluids

AP 5.1 Racing exceeds DOT 5.1 but IS compatable with other fluids

You must read the labels and the Spec sheets to be sure of compatability. DOT rating does not render any info or guarantee concerning compatability.

Furthermore my understanding of the difference between a DOT 4 fluid and Super DOT 4 fluid is that they both meet DOT 4 specs. The "Super" fluid is usually associated with the fluids ability to remain stable, longer, under high heat conditions and not deteriorate chemically. It has NOTHING to do with Boiling Points which IS the prime consideration.

The term "synthetic" usually denotes that NO organic base stock was used to manufacture the product. Synthetics are usually better products in that they do not degrade as fast. The usually cost more because they are more difficult to manufacture. In most all cases a synthetic should be choosen over a non synthetic for performance, protection and stability. The only exception is when a non-synthetic is called for to break in a particular system such as mineral oil to break in an aircraft engine during the 1st 50 hours of operation or when the technique of reseating rings calls for "use straight SAE 30 weight Kendall racing oil".

The use of "synthetic" with brake and clutch fluids is kind of a misnomer because I do not know of any good brake fluid that contains organics.....IE they are all "synthetic". "Synthetic" use in labeling is true but is probably a marketing ploy.

[No Doubt]

Although AP Racing states...

"It should be noted that before using AP Racing PRF 660 fluid, any existing brake fluid should be drained completely from the brake system. The system should be thoroughly purged with new AP Racing PRF660 brake fluid and can then be filled completely with AP Racing 660 fluid."

Note that AP Racing does not explicitly state their AP Racing PRF 660 is chemically incompatible with other fluids. It may be they can't insure their fluid will perform up to specification when mixed with other fluids. I may be wrong about that, but I have seen no proof to the contrary. I have emailed AP Racing for clarification.

Again, "Super DOT 4" is not a DOT specification. It is a marketing term only. DOT 5.1 on the other hand IS a specification. "Super DOT 4" is often a glycol ether and borate ester based fluid (the same as DOT 4), but may exceed the minimum DOT 4 specification which are also typically glycol ether and borate ester based fluids, as I stated above.

Think of "Super DOT 4" as a DOT 5.1 fluid, chemically (typically a glycol ether and borate ester base), but that does not meet the DOT 5.1 boiling point specifications. Hence, it can not be labeled or marketed as such. "It's better than DOT 4 but not as good as DOT 5.1 so we'll call it "Super DOT 4." You have to love marketing.

Originally Posted by D J Worm

DOT rating does not render any info or guarantee concerning compatability.

It's true that FMVSS # 116 has no requirements for the chemical compounding of brake fluids and only dictates the fluids physical properties. However, the brake fluid industry as a whole has agreed that glycol ether based fluid is the most economical way to meet the federal requirements for DOT 3 brake fluids. The same goes for DOT 4 fluids which, in addition to glycol ether, include borate esters as a means to increase boiling points, with some exceptions. Castrol SRF for example utilizes unique and patented chemistry.

Originally Posted by DJ Worm

The use of "synthetic" with brake and clutch fluids is kind of a misnomer because I do not know of any good brake fluid that contains organics.

All glycol ether and borate ester based brake fluids, which comprise the majority of DOT 3 and DOT 4 fluids, are indeed organic (mineral based) compounds. They are not man-made synthetic compounds. Note also that all AP Racing brake fluids are polyalkylene glycol ether based fluids (an organic compound).

[DJWorm]

This article discribes what has happened in the engine oil marketing circles regarding "Synthetic".

What "synthetic" means inregards to brake fluid is anyone's guess.

Synthetic Definitions of Synthetic Lubricants

[george]

Originally Posted by Tom Slick

I went to Wallyworld to get some filters for my truck and some fluid for the clutch in the Z. The owners manual says to use Super DOT4 brake fluid in the clutch reseviour (sp), but all that I could find was Prestone Synthetic DOT4 brake fluid. I went to Auto Zone and Kragen and all they had was the Synthetic DOT4. I went to Chevy and they had the Super stuff, but for 16oz it was $8.00. The Prestone stuff was only $2.98 for 32oz. I'm not cheap, but if I can use the Synthetic stuff in lieu of Super I'll go that route.

Is there a difference other than GM calls their DOT4 fluid Super. Shouldn't all DOT4 fluids be compatible?

Oreilly's Auto Supply sells DOT#4 Non Synthetic (reg) by the quart. Just keep changing that fluid when it turns a Tea color in the engine bay reservoir. Watch the paint job.

[No Doubt]

Is H2O (water) synthetic? Of course not, however, when Chlorine and Fluoride for example are added it becomes a man-made "synthetic" compound because, according to the ruling you speak of, it's not found in nature that way.

The same can be said for steel and aluminum. Neither is a naturally occurring substance. They are man-made compounds, but contain naturally occurring mineral ores as their bases. In this case, iron ore and Bauxite, respectively.

The same can be said for "synthetic" oils and brake fluids. The base stocks mentioned above are naturally occurring organic compounds, but other chemicals may be added to the point the resulting substances are no longer found in nature. Hence the term "synthetic" is allowed and used.

[augydog]

Originally Posted by No Doubt

Is H2O (water) synthetic? Of course not, however, when Chlorine and Fluoride for example are added it becomes a man-made "synthetic" compound because, according to the ruling you speak of, it's not found in nature that way.

The same can be said for steel and aluminum. Neither is a naturally occurring substance. They are man-made compounds, but contain naturally occurring mineral ores as their bases. In this case, iron ore and Bauxite, respectively.

The same can be said for "synthetic" oils and brake fluids. The base stocks mentioned above are naturally occurring organic compounds, but other chemicals may be added to the point the resulting substances are no longer found in nature. Hence the term "synthetic" is allowed and used.

No Doubt, I think Aluminum is a natural substance in nature.

augydog

Name: Aluminum
Symbol: Al
Atomic Number: 13
Atomic Mass: 26.981539 amu
Melting Point: 660.37 °C (933.52 K, 1220.666 °F)
Boiling Point: 2467.0 °C (2740.15 K, 4472.6 °F)
Number of Protons/Electrons: 13
Number of Neutrons: 14
Classification: Other Metals
Crystal Structure: Cubic
Density @ 293 K: 2.702 g/cm3
Color: Silver

[DJWorm]

The point of the article is that NO particular agency, society or organization specifies the definition, "allows" or regulates the use of "synthetic". It means different things to different people. Mobil 1 tried to ajudicate the issue V. Castrol but was defeated.

It therefore is a loose dictonary definition and is used many ways in marketing a product. One needs to look at the fluid spec. sheet and MSDS to get a clear picture of a particular manufaturers use of "synthetic".

A synthetic fluid may contain organic base stocks, inorganic base stocks, be refined or be an organic distillate. All of the above or none of the above. Synthetic may denote the ORIGIN of the base stock or the finished product OR the PROCESS from which it was made.

Although the alkides used for the base stock of brake fluids are by products of oil refining (distillates of gasoline refining) I consider them to all be synthetic due to their non-natural occurance and the further synthesis used in their manufacture. Some manufacturers such as Valvoline label theirs as synthetic where as AP doesn't...but they are all similar. The difference is in the minimum DOT standard that they must meet as to wet & dry boiling points. Wether or not a brake fluid is labeled "synthetic" is almost irrelevant and is only a marketing ploy.

Wether or not it is compatable with other brake fluids has nothing to do with it's DOT ranking OR wether or not it is labeled synthetic or not.

I can tell you for sure that DOT 4 AP 600 and DOT 4 AP PRF 660 being Polyalkylene glycols are NOT compatable with any other brake fluids which are Borate or Glycol derivitives. In fact they are not even compatable with each other.

Again, even if both fluids might be compatable with each other, fluids with different wet & dry boiling points should never be admixed even though they can be. I would only do so in an emergency situation when the original fluid is NOT available.