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What’s the Difference Between DOT 3 and DOT 4 Brake Fluid?

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What’s the Difference Between DOT 3 and DOT 4 Brake Fluid?

John Baker|

The primary difference between Dot 3 and Dot 4 is their respective boiling points.

I suspect I know your next question.

But first, some background. The U.S. Department of Transportation classifies brake fluid into four main categories:

  • DOT 3
  • DOT 4
  • DOT 5
  • DOT 5.1

Their primary differences are their wet & dry boiling points and their composition.

DOT 3 is the most common type used in cars and trucks today. DOT 4, however, is gaining popularity due to widespread use of anti-lock braking systems and traction control, which benefit from DOT 4 fluid’s lower viscosity.

DOT 4 is compatible with DOT 3, but features a higher boiling point. DOT 5 is silicone, meaning it doesn’t absorb water. It’s not compatible with the other brake fluids and is used mostly in classic cars that remain in storage for long periods and need a brake fluid that doesn’t absorb water. DOT 5.1, meanwhile, is used in high-performance and heavy-duty applications due to its high boiling point.

Bring it to a boiling point

So now we’re back to boiling point. What does it mean? After all, we’re not cooking this stuff.

Well, in the right operating and ambient conditions, you are cooking it.

Aggressive braking can lead to intense heat.

Braking generates intense heat between the brake pads and rotors. Maybe you’ve seen a race on TV where the producers stick a GoPro under the car to show the brakes literally glowing red when the driver depresses the pedal. The intense heat can vaporize the brake fluid, causing it to become compressible, which leads to a spongy feeling when you apply the brakes.

Braking also places the fluid under intense pressure, potentially causing the fluid to boil. That leaves gas in the lines, which is compressible, leading to a soft pedal. In racing and performance-driving circles, this is known as brake fade, and it’s something drivers actively want to avoid. To drive as effectively and safely as possible, the driver must be confident that the brakes will perform on lap 10 as they did on lap one.

Brake fade can also come from the brake pad/rotor interface. The pads release gasses as well, which reduces contact between the pads and rotors. That’s why high-end rotors are slotted and drilled – to release gasses quicker, limiting fade.

Brake fade isn’t just for racers

Brake fade can affect nearly anyone. Descending a steep hill, especially when hauling a heavy load or towing a trailer, can generate tremendous heat if you ride or pump the brakes.

PRO TIP: Next time, downshift into a lower gear before descending a steep incline.

By the time you reach the bottom, your pedal may go nearly to the floor, making your heart rate go nearly through the roof.

If you like to toss your vehicle around a curvy country road for a little therapy, standing on the brakes going into corners can create sufficient heat to cause brake fade, too. If you get a little too zealous, you may end up going right through a corner and into the woods.

The fluid’s boiling point indicates the temperature at which the brake fluid vaporizes. The higher the DOT classification, the higher the boiling point, thus the better the fluid is at resisting heat. That’s why racers use DOT 4, not DOT 3, brake fluid.

Boiling point is separated into dry & wet boiling points

The dry boiling point is determined using fresh fluid straight from a new container. The fluid’s wet boiling point is determined using fluid that’s been contaminated with 3.7 percent water, thus it’s always lower than the dry boiling point. Why would test administrators contaminate good fluid? Because it’s a reflection of what happens in the real world.

Brake fluid is hygroscopic, meaning it absorbs water (except silicone-based DOT 5 brake fluid). DOT 3 fluid, for example, can absorb up to two percent water every year. Moisture can enter the system when you remove the reservoir cap to add fluid, through worn seals and even through the rubber brake lines themselves. Thus the fluid’s wet boiling point is the number that more accurately represents what’s really going on in your vehicle.

Which makes it important to periodically flush the brake system and replace the fluid to remove moisture. Otherwise, not only will your brakes become spongy and unsafe, the moisture will slowly corrode metal components.

A good rule of thumb is to change the brake fluid every other year in passenger vehicles, and at least every year in racing vehicles. The AAA says 88 percent of motorists overlook brake maintenance, so you’re not alone if you haven’t changed brake fluid in awhile, like since you bought your vehicle.

It’s not too late to start, though. And when you do, check out our line of brake fluids for your vehicle. The easiest way to determine the correct brake fluid for you vehicle is to use our Product Guide.

Find AMSOIL Brake Fluid for my Vehicle

Sioux Falls Webmaster note: AMSOIL’s Dot 4 outperforms it’s new 5.1 because the 4 is designed purely as a racing brake fluid where as the 5.1 id the latest for all uses yet still beyond the minimum standard.

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New ATV/UTV Oil Change Kits Offer Maximum Convenience

Written by Charleen
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New ATV/UTV Oil Change Kits Offer Maximum Convenience

AMSOIL ATV/UTV Oil Change Kits combine everything needed to perform an oil change on the most popular models of Polaris* ATVs and UTVs in one convenient package, including…

To find the correct ATV/UTV Oil Change Kit for your machine, consult the appropriate Product Guide.

Look up My ATV

Look up My UTV

WHY YOU SHOULD UPGRADE YOUR ATV/UTV PROTECTION

Accessories equal weight. It’s common to burden your UTV or ATV with accessories designed to increase power or productivity, especially for UTV owners. Enthusiasts often add roof and door panels, a winch, a plow, skid plates and other accessories. Plus, how often do you haul a load of gravel or pull a trailer or other implement?

This all adds weight, and a good rule of thumb is that extra weight equals extra heat. Heat, in turn, causes lubricants to break down sooner, which places your engine and differentials at risk of wear.

Heat invites engine wear. The oil’s primary job is to form a protective layer on metal parts to keep them separated so they don’t rub together and wear out. High heat from the stress you place on your machine, however, can cause oils formulated for standard service to become thinner (lose viscosity). Oil that has lost viscosity can fail to develop an oil film of adequate thickness or strength to protect against wear.

Plus, high heat invites sludge and performance-robbing deposits inside the engine. Sludge can clog oil passages and starve the engine of oil, while deposits can cause the piston rings to stick or interfere with proper valve operation, leading to reduced engine compression.

Since compression equals power, over time your engine can make less power, limiting your ability to ride or work as effectively as possible. Eventually, deposits and sludge can wreck the engine completely.

Shift to better performance. The story is similar inside the transmission, differential and front drive. All the extra weight and stress of hard work and performance riding concentrates intense pressure on gears. The lubricant coats the gear teeth during operation, guarding against metal-to-metal contact and wear. The added stress, combined with high heat, can break the fluid film and literally squeeze the lubricant from between the gears, leading to wear. As with the motor oil, high heat causes the lubricant to thin, which negatively affects wear protection.

Upgrade to synthetic lubricants. So what’s the solution? Ride more conservatively? Haul lighter loads and work less?

Never. Upgrade to high-quality AMSOIL synthetic motor oil, differential and transmission fluid, front drive fluid and other lubricants, especially if you’ve modified your ATV or UTV for greater power or productivity. AMSOIL synthetic ATV/UTV lubricants don’t contain the impurities inherent to conventional lubricants, meaning they deliver better performance and last longer. Their naturally tough base oils resist extreme heat and maintain a strong protective film better than conventional products.

Think of synthetics as just another performance upgrade. You don’t think twice about dropping a few hundred dollars on a snowplow or work trailer. Over the course of your machine’s life, the few extra dollars you spend per oil change or transmission/differential service is a drop in the bucket by comparison.

*All trademarked names and images are the property of their respective owners and may be registered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use. All products advertised here are developed by AMSOIL for use in the applications shown.

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Transmission Pan Drop vs. Flush: Which is Better?

Written by Charleen
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Transmission Pan Drop vs. Flush: Which is Better?

John Baker|

It depends on what you want to accomplish. But, first of all, check your owner’s manual to see if your vehicle manufacturer recommends one instead of the other.

If you want to ensure removal of nearly all the old transmission fluid, then have your transmission flushed.

Here’s what we’ll cover:

What is a Transmission Flush?

The benefits are self-evident: all the old, dirty fluid is replaced with fresh, high-quality fluid. (And, as you can see in the image, new transmission fluid is preferable to old fluid). As a result, your transmission should run cooler and receive maximum protection against wear to clutches, gears and bearings. It should also shift consistently and crisply since the new fluid will provide the correct frictional properties (old fluid loses its frictional properties over time).

Not only that, but performing a flush helps clean the transmission. Sludge and other contaminants can accumulate in the fluid due to extreme heat breaking down the fluid. These contaminants circulate throughout the transmission before lodging in the filter. Before the filter can safely capture the contaminants, however, they can lodge in the narrow fluid passages inside the valve body, leading to poor shift quality.

The narrow fluid passages in the transmission valve body can easily clog with debris, reducing shift quality.

Performing a flush also allows you to use a flush additive to help clean the transmission and more effectively remove accumulated sludge and other contaminants.

Any downsides?

Potentially.

For one, it’s more expensive. And some people warn against performing a flush on a transmission using old, dirty fluid. The flushing procedure may direct the fluid in the opposite direction of normal flow, which may increase the risk of dislodging debris and causing it to settle somewhere it shouldn’t. Since the way each shop performs a flushing procedure varies, you can’t know for certain.

What is a transmission flushing machine?

A typical flushing machine uses hoses that connect into the transmission cooling lines. It drains the old fluid and holds it inside the machine while replenishing the transmission with new fluid. Unlike a simple pan drop, a flushing machine removes just about all the old fluid, including the fluid inside the torque converter.

Since the procedure uses new fluid to perform the flush, it requires several quarts of new fluid beyond the transmission’s final capacity. Those extra quarts are where most of the added cost lies.

(Find out how an automatic transmission works.)

The good ‘ol pan-drop

If you have reservations about a flush, go with a pan-drop instead. While it reduces the risk associated with flushing old, dirty fluid through the transmission, a pan-drop also has downsides.

  • Removes only about a third of the fluid
  • Can be a mess
  • Can be a pain on some vehicles

I can tell you from experience that a pan-drop can be a bigger job than you think. You may have to remove plastic splash guards or metal skid plates to access the transmission pan. In case you haven’t been under your vehicle in a while, plan on encountering rusted, stuck bolts if you drive in wet, snowy conditions. Don’t be surprised if you crack a splash guard in one or two places as you try to remove/reinstall it.

Tips for performing a pan-drop:

  • Have a large catch pan handy. Otherwise, once you loosen the pan bolts, fluid is going to ooze from the pan/transmission interface and end up all over the floor.
  • If you’re crafty, you can back out the pan bolts in one corner further than the surrounding bolts, effectively tilting the pan so the fluid drains from a single corner instead of overflowing the entire pan. This reduces mess quite a bit.
  • Wear safety glasses and gloves.
  • Don’t forget the new filter and pan gasket.
  • It’s a good idea to know the torque specs on the pan bolts and use a torque wrench to reinstall them. Otherwise you risk overtightening and ruining the gasket.

You might get lucky, though

Some vehicle manufacturers install a drain plug on the transmission, similar to a motor oil drain plug. This allows you to easily and cleanly drain some fluid from the transmission minus the hassle of removing the pan. Again, though, you only get a third to half the fluid out.

You can then drive the vehicle for a while, then drain the fluid and change it again. Do this 2-3 times and you’ll remove nearly all the old fluid and perform a sort of poor-man’s transmission fluid flush.

Bottom line: Visit a pro and have the transmission flushed for best results and least hassle (unless your vehicle manufacturer specifically warns against it in the owner’s manual). But, if you have reservations about dislodging debris due to old, dirty fluid, a series of pan drops works just as well.

FIND AMSOIL TRANSMISSION FLUID FOR MY VEHICLE

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Why Did We Reformulate Signature Series Synthetic Motor Oil?

Written by Charleen
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Why Did We Reformulate Signature Series Synthetic Motor Oil?

Local Sioux Falls note: We are reposing this article from last fall as it is important to realize the changes coming and how these enhancements will only add to the performance on older vehicles too.

AMSOIL’s Signature Series likely already exceeds the future API specification which hasn’t rolled out yet and we know other larger competing lubricant companies are having issues with LSPI (read more below).

John Baker|

Simply put, we reformulated Signature Series Synthetic Motor Oil to solve problems.

For all the derision heaped upon the internal-combustion engine, it remains our primary mode of propulsion. And, despite the gains of hybrids and electric vehicles, it will remain so for the foreseeable future.

One reason is the tremendous efficiency gains gas and diesel burners have made since the 1970s. The loud, proud cast-iron powerplants of yesteryear may still quicken your pulse when they roar past powering a hot rod or classic car, but they can’t match the fuel economy and reduced emissions of the engine likely powering the vehicle you drove to work today.

That’s due to the widespread use of turbochargers, direct fuel injection, variable valve timing and lightweight materials.

But, despite their many benefits, modern engines present several challenges, and it’s up to the motor oil to solve them.

Four little letters, one big problem

One of the biggest is low-speed pre-ignition (LSPI). If you read the AMSOIL blog, you’ve heard about LSPI by now. LSPI is such a big deal that it’s the driving force behind the next generation of motor oil performance specifications.

In a nutshell, LSPI is the spontaneous ignition of the fuel/air mixture prior to spark-triggered ignition. It occurs in modern turbocharged, gasoline-direct-injection (T-GDI) engines, and it’s another version of pre-ignition, which has been around since engines were invented. In this case, though, it occurs under low-speed, high-torque conditions and is much more destructive than typical pre-ignition.

Computers to the rescue

Automakers can program their vehicles to avoid operating conditions that invite LSPI. The problem, though, is that programming the engine to operate on that “ragged edge” that invites LSPI promises fuel economy gains of up to 10 percent.

With CAFÉ standards looming, automakers are eager to realize those efficiency gains.

But they can’t until motor oils hit the market that help prevent LSPI. Motor oil formulation plays a big role in fighting LSPI, so much so that the next generation of motor oil specifications requires oils to pass an LSPI test. The forthcoming API SP and ILSAC GF-6 specifications aren’t scheduled for introduction until fall 2019, however.

Some automakers have grown impatient and have requested that the API, which licenses ILSAC GF-5, supplement the current specification with an LSPI test requirement. That could happen as early as January, 2018.

General Motors is ahead of the game. Its proprietary dexos1® Gen 2 spec, introduced in August, includes an LSPI test.

An oil that solves problems

Which brings us back to Signature Series. We want our flagship motor oil to stand alone as the best motor oil in the world, and preventing LSPI is one prerequisite to achieving that goal.

So we subjected it to an LSPI engine test.

The result? Signature Series Synthetic Motor Oil provided 100 percent protection against LSPI* in the engine test required by the GM dexos1 Gen 2 specification.

In short, the oil solves a major problem plaguing the industry right now.

But wait, there’s more…

What about the old standbys, like engine wear and extreme heat?

Here, too, Signature Series excels.

From the day your engine fires to life, friction tries to wear away bearing surfaces, cylinders, piston rings and other components. Left unchecked, it’ll render your pride and joy a gutless, wheezing shadow of its former self. Eventually, something can break completely.

We formulated Signature Series to deliver next-level wear protection. But we know you want proof, not promises.

In the API Sequence IV-A Engine Wear Test required for the API SN specification, Signature Series delivered 75 percent more wear protection than required**.

What does that mean for you?

An engine that lasts for years and delivers maximum horsepower long after you’ve made the final payment. To prove it, we installed Signature Series 5W-30 Synthetic Motor Oil in a Ford F-150 with a new 3.5L Ecoboost engine to test its ability to protect turbocharged direct-injection engines from torque and horsepower loss during extended drain intervals up to 25,000 miles. Power sweeps were done at the beginning and end of the test to evaluate horsepower and torque retention. As the graph shows, Signature Series helped maintain engine performance throughout the 100,000-mile test.

Fights engine deposits

Engine deposits, too, do their best to sideline your vehicle. High heat can breakdown motor oil, leading to piston ring, piston crown or valve deposits, which erode horsepower and efficiency. In severe cases, your engine can fail altogether.

Heat is more prevalent in T-GDI engines. Turbos run on exhaust gases that can exceed 1,000ºF and can spin more than 150,000 rpm. The turbo’s center section contains an oil-lubricated bearing. The tremendous heat and stress turbos create can cause some oils to break down and form harmful bearing deposits, known as turbo coking. Over time, turbos can suffer reduced performance, or fail completely.

Again, Signature Series solves the problem of extreme heat. We challenged Signature Series to the GM Turbo Coking Test, which consists of 2,000 cycles of extreme heat soaks. An oil must limit the temperature change within the turbocharger to 13 percent or less to pass the test. Signature Series limited the temperature increase to only 3.6 percent, protecting the turbocharger 72 percent better*** than required by the GM dexos1® Gen 2 specification.

Signature Series controlled heat and minimized performance-robbing deposits on the turbo bearing and shaft surfaces.

And, lest we forget, the performance of Signature Series Synthetic Motor Oil lets you extend drain intervals to 25,000 miles/one year if you choose, even in turbocharged engines.

With challenges to engine protection and performance mounting – and new problems cropping up – it’s vital we stay one step ahead.

That’ll help you continue to get the best protection and most years out of your vehicles.

BUY SIGNATURE SERIES SYNTHETIC MOTOR OIL

* Based on independent testing of AMSOIL Signature Series 5W-30 motor oil, in the LSPI engine test as required for the GM dexos 1® Gen 2 specification.
** Based on independent testing of AMSOIL Signature Series 0W-20, in ASTM D6891 as required by the API SN specification.
*** Based on independent testing of AMSOIL Signature Series 5W-30 in the GM turbo coking test.

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