AfterMarketNews AfterMarketNews Auto Care Pro AutoCareCareerHub Brake&Frontend BodyShopBusiness Counterman EngineBuilder Fleet Equipment ImportCar Motorcycle & Powersports News Servicio Automotriz Shop Owner Tire Review Tech Shop Tomorrow's Tech Underhood Service Speedville

Top 10 Brake Job Mistakes For Pads, Rotors And Calipers

Here are the top 10 brake job mistakes made by rookie technicians when replacing brake pads, rotors and calipers.   10. Not cleaning the brake slides and hardware: Just slapping new pads where the old pads once resided never works. The...

Read more...

Snap-on Brightens Up Your Workspace With New Rechargeable Shop Light

Get out of the dark and brighten up your workspace with the new Snap-on ECFBAR300 Rechargeable Shop Light. With an innovative Chip-On-Board LED efficiently delivering more light while maximizing battery power, this powerful shop light is ideal for use...

Read more...

Ingersoll Rand's 'Real Work Real Play' Sweepstakes With Gas Monkey Garage And NASCAR Rewards A Tool User With The Ultimate Fan Weekend

Ingersoll Rand, the Official Power Tools of NASCAR and a preferred tool provider for Gas Monkey Garage, has announced the “Real Work Real Play” sweepstakes to reward automotive fans who “get it done” with a weekend of fun. Ingersoll Rand is working...

Read more...

The Element of Trust And Its Impact on a Repair Scenario

Trust: It’s an important word, and it’s one I hear a lot behind the counter at the shop. “I know you’ll treat me right because I trust what you do,” is the general sentiment. But I’ve always wondered how deep that level of comfort goes...

Read more...

Servicing Mercedes-Benz AIRMATIC Suspensions

The Mercedes-Benz AIRMATIC suspension system was introduced in 1999 on the S-Class and has subsequently been used on the E-Class and most of the automaker’s SUVs. The system employs electronically controlled air springs that provide an ideal balance...

Read more...

Nissan: Solving Performance & Check Engine Light Issues

We recently had a late-model Sentra towed in with a no-crank complaint. This was the first time we were faced with a smart-key-equipped Nissan that did nothing when the start button was pushed. My first step on any diagnosis is to put the enhanced scanner...

Read more...

Ingersoll Rand's 'Real Work Real Play' Sweepstakes With Gas Monkey Garage And NASCAR Rewards A Tool User With The Ultimate Fan Weekend

Ingersoll Rand, the Official Power Tools of NASCAR and a preferred tool provider for Gas Monkey Garage, has announced the “Real Work Real Play” sweepstakes to reward automotive fans who “get it done” with a weekend of fun. Ingersoll Rand is working...

Read more...

Bosch Relaunches Boschdiagnostics.com With Mobile-Responsive Design, New Layout For North America

Bosch has announced the re-launch of boschdiagnostics.com in North America, continuing to update all of its sites to a mobile-responsive, intuitive design. The URL contains three separate sites, featuring DIY diagnostic tools (DIY), professional diagnostic...

Read more...

New Bartec Tech400Pro TPMS Tool To Be Demonstrated At NACE | CARS

Bartec USA, a North American leader in TPMS Diagnostic tools, will hold live demonstrations of its newly released Tech400Pro TPMS Scan Tool at this year’s NACE | CARS show in Detroit. Michael Rose, Bartec product manager, will conduct these demonstrations...

Read more...

BMW Recognized for Engine-Building Excellence

BMW Group’s engine-building prowess was recognized with four wins at the latest International Engine of the Year Awards. The drive unit in the BMW i8 earned two class wins as well as being declared overall winner, with a further class win being garnered...

Read more...

Diagnostic Dilemma: The Case of the Missing Code

When doing mobile diagnostic work, no-code stalling complaints are a major part of your agenda. In most cases, the client shop is simply too busy to duplicate the failure or, in some cases, a long test drive will yield nothing in the way of useful...

Read more...

Secondary Ignition: The Art of Spark

What is a coil? From the beginning of the internal combustion engine, several different ignition systems have been used to create a high-energy spark. The most popular system, and the one that’s in use today, is a step-up coil. A coil is nothing...

Read more...

Home Brakes Brake Fluid Q & A

Print Print Email Email

Mike Evangelo of Dynamic Motorsports and Rossion Automotive e-mailed me with six questions about brake fluid. I like a challenge, so here are my answers.

1. What are the fundamental differences between synthetic fluid and conventional DOT 3 and 4?
Simple, it all comes down to the base stock. Both synthetic and conventional brake fluids start from the same “polyethylene glycol” stock. But, to make synthetic brake fluid the manufacturer will “synthesize” the original base stock and make the molecules better and more consistent. They could make the chains longer or add other molecules to enhance the performance. Almost every synthetic brake fluid manufacturer does it different.

To the base stock they add the additive package. This is a mixture of anti-corrosion, anti-foaming and other secret chemicals that give the fluid the desired performance characteristics for operation in vehicles.

DOT 5.1 is a high-performance certification (higher temps than DOT 5). To meet the performance criteria, it takes a synthetic or really good conventional base stock.

Silicone is a synthetic substance. But, don’t confuse Dot 5 with synthetic polyethylene glycol-based fluids like DOT 5.1.

2. What is the compatibility between synthetics and conventional DOT 3 and 4 in most vehicles?
Is a complete flush with new rubber a better choice? Is there any chance of seal swelling or disintegration in older vehicles say from the 1930s, 1940s or even in the 1960s?

All DOT 3, 4 and 5.1 brake fluids are compatible with each other and with all systems. All polyethylene glycol-based fluids will not harm healthy rubber parts. Also, the additive packages will not damage or distort any rubber parts. Even if an older rubber part that has a high concentration of natural rubber, they will not be damaged by new DOT rated brake fluids.

What kills rubber parts is when the additive package breaks down. The additive package controls the pH of the fluid and the viscosity. If the brake fluid becomes unable to control the pH or other corrosive elements, the rubber and metal parts will deteriorate over time.

If you have an older vehicle and are worried about boiling the fluid, use DOT 4 or 5.1 brake fluid.

3. Can synthetics be mixed where DOT 5 silicone was used or is it recommended that the rubber be replaced when changing back?
Silicone is an inert substance, this is why it is safe for breast implants. Technically it should not damage the rubber parts.

Polyethylene glycol based fluids (conventional or synthetic) will not mix with silicone fluid (DOT 5). It will lump together somewhere in the system. Also, they will not react when it is mixed. So, if you perform a good flush, the rubber parts and the system should be OK..

4. Now that it is known that copper contamination is the main reason that brake fluids degrade, what property do synthetics have to address this problem?
Copper comes from the copper brazing in the walls of the hard brake lines. copper can be a problem for ABS and some valving. But, it is an indicator of the state of the brake fluid. The more copper that is present, chance are greater that corrosion is happening in the system. When there is corrosion, it is a sign that the brake fluid’s anti-corrosion additives are depleted.

If your base stock and additives are of higher quality, chances are that they will not break down as easily as low-quality ingredients.

5. Compared to conventional fluid what life span can be expected from synthetics?
In my opinion, it is about the same. Synthetic fluid might be able to last a little longer because the fluid can absorb more water before the fluid drops below a critical boiling point. But, it is the additive package and environment that has the greatest impact on life span, no matter what type of base stock.

6. Some have said that they have noted a better pedal feel with synthetic fluids. Is this possible?
Some very high-end synthetic DOT 4 and 5.1 synthetic fluids can give a better pedal. But, it is so small of a difference that only the very, very, very best drivers can feel it. It is mostly in their head.

Some silicone-based fluids can give a softer pedal because it is more compressible than glycol-based fluids. But, some high-tech silicone ester-based stuff that some race teams use is less compressible than glycol-based fluids. But, this stuff can run $90 a liter! Also, it does not have some critical corrosion inhibitors and is not DOT certified.

DOT 5 brake fluids still have their place. Owners of show cars can use the fluid if they are concerned about damage to the paint.

Thanks Mike!

The following two tabs change content below.

Andrew Markel

Andrew Markel is an ASE Certified Technician and former service writer, and he brings this practical knowledge to the Brake & Front End team as editor.
Latest articles from our other sites:

The Element of Trust And Its Impact on a Repair Scenario

Trust: It’s an important word, and it’s one I hear a lot behind the counter at the shop. “I know you’ll treat me right because I trust what you do,” is the general sentiment. But I’ve...More

Check Out The July Issue Of Underhood Service Magazine

The digital version of the July issue of Underhood Service is available on-line. CLICK HERE to access the easy-to-view digital version that features articles on Cooling System Technology, Starter And...More

The Element of Trust And Its Impact on a Repair Scenario

Trust: It’s an important word, and it’s one I hear a lot behind the counter at the shop. “I know you’ll treat me right because I trust what you do,” is the general sentiment. But I’ve...More

Servicing Mercedes-Benz AIRMATIC Suspensions

The Mercedes-Benz AIRMATIC suspension system was introduced in 1999 on the S-Class and has subsequently been used on the E-Class and most of the automaker’s SUVs. The system employs electronically controlled...More

Atlas Copco USA Continues Long-Standing Partnership With Stewart-Haas Racing

Atlas Copco USA has announced it will continue its longstanding partnership with Stewart-Haas Racing (SHR), a NASCAR Sprint Cup Series team co-owned by three-time Sprint Cup champion Tony Stewart and...More

BendPak-Ranger Introduces 3D Wheel Alignment System

Ranger Products recently introduced its new Target 3DPro 3D Imaging Wheel Alignment System for domestic and import cars and trucks. Lightweight impact-resistant wheel targets and high-resolution tower-mounted...More

Top 10 Fuel Pump Fails

10. Strainer Blocks Fuel-Level Sender A fuel pump inlet strainer may be installed that is interfering with the travel of the fuel-level sensor’s float arm, which causes an optimistic fuel level...More

GMC Yukon No-Cranking Complaint: The 1,300-Mile Test Drive

This month’s Diagnostic Dilemma is about the technical and professional issues involved with attempting to diagnose an extremely random no-cranking complaint on a 2003 GMC Yukon equipped with the 5.3L...More