Castrol SRF VS Motul 660: Which Is The Best Brake Fluid

Want to choose a brake fluid for your vehicle? Well, we know it’s a very worrying and confusing matter. Choosing the best brake fluid means it’s directly connected with your safety. Castrol SRF vs. Motul 660 which one is suitable for the braking system. Nowadays, Castrol SRF is the famous brake fluid in the market.

Frequently, you don’t need to change these Castrol SRF fluids and create a price-efficient of this fluid. Consequently, if you want the best budget fluid, Motul 660 can be your best choice.
Here we have given just a summary of the entire discussion. Read this whole article before making the best decision.

Castrol SRF vs Motul 660: Which Brand Is Better?

Now here, we will discuss two detailed brand comparisons. We have broken down both categories and tried to describe them quickly.

  • Moist Boiling Point

This is the parameter of every brake fluid. Basically, this is the temperature where brake fluid boils after sucking 3.7 percent water. A higher grade means brake fluids have good longevity. Likewise, there are many differences between Castrol SRF and Motul 660.

Castrol SRF temperature is at 270°C or 518°F and Motul 660 temperature is at 204°C or 399°F. However, this wet boiling point is discursive if you frequently flush the brake. Generally, if you want to use brake fluid for everyday driving, you can use Castrol SRF. But the demanding driver can use both of this oil easily.

  • Waterless Boiling Point

Waterless boiling point is critical feature for racers. It’s a brake fluids temperature when fresh, new, and uncovered. Generally, this is the highest temperature, and oil will not disintegrate at this temperature.

That means this highest dry boiling temperature is best for oil. In this case, Motul 660 has extreme waterless boiling temperature. In contrast, Castrol SRF also has this standard, and the temperature is 590°F or 310°C. Subsequently, if you want to dry the boiling point higher, Motul 660 can be the best brake fluid for them.

  • Changing Frequency

Changing the frequency of brake fluid means how often you flush your brake fluid. Consequently, it usually depends on your purpose. Now, you may love to use your vehicle on the race tracks.

The lower wet boiling point makes it more reliable. While using Motul 660, you don’t need to change this oil as often as you need.

In every season, you will change this brake fluid twice. But you can use both oils on the road. After discussion, we know Castrol SRF is best from Motul RBF 660. Most importantly, to reduce the costs, this lower changing frequency plays a big part.

  • Price Point

Everyone is always thinking about price when they are buying something. Spending additional money is not a wrong decision to pick the best product. Mainly, Motul 660 price is 54$ per liter, Castrol SRF price is 74.5$ per liter.

At last, after knowing the price, you must want to pick Motul 660. Before making the right decision, please remember about changing frequency. We have discussed earlier that you need to frequently change Motul 660 brake fluid than Castrol. Hence, this makes Motul 660 brake fluid more costly than Castrol SRF.

Castrol SRF vs Motul 660: At a Glance

BrandCastrol SRFMotul 660
Item Weight2.02 pounds1.28 pounds
Product Dimensions‎11.02 x 7.19 x 3.24 inches3.3 x 7.25 x 2.15 inches
Liquid Volume1 Liter500 Milliliters
PerformanceHigh-performanceBetter aerodynamic performance
Car typeRacing carCar, Motorcycle
Dry boiling point310 °C312 °C
Wet boiling point269 °C205 °C
Price Range$74.95$54.85

Castrol SRF Wins

Castrol Srf brake fluid is hands down the best “performance” brake fluid for the money. Below we will discuss these brake fluids’ advantages and disadvantages. So, please read on to know about them deeply.

Castrol SRF Wins
Overall Rating
  • High Dry Boiling Point:

SRF brake fluid’s high dry boiling point creates this fluid ideal for use under difficult braking situations like racing. Actually, this feature can exceed the dot-5 fluids boiling point requirements.

SRF brake fluids are ideal for serving road cars and trucks. It’s because, over 1-2 years, after absorbing 3.7% water, these fluids can survive with tough drive.

  • High-Performance Brake Fluid:

The Castrol SRF compressibility is the same as the current DOT 3 and Dot 4 brake fluids. Therefore, Castrol is ideal for all drum and brake systems where mineral oil is determined.

After using this brake fluid, you can feel a “hard pedal. Notably, this is a fantastic Castrol product registered under patents in several countries. Most importantly, they exceed specifications of US Federal standards FMVSS 116 Dot 4 and Dot 3, JIS K2233, and more.

  • High-Vapor Lock Point:

Castrol comes with a high vapor lock point and extra benefits of maintaining these characteristics during its service life. Even so, you can use this brake fluid in any non-mineral oil braking system.

Castrol Losses

The Castrol SRF brake fluid losses are:

  • Don’t Mix Conventional Oil:

In contrast, if you use conventional brake fluid with Castrol SRF, this mistake can reduce the quality of this Castrol SRF brake fluid. That’s why, before refilling with Castrol SRF, you should drain the conventional brake fluid very well.

  • Expensive:

Specifically, Castrol SRF is quite costly than other brake fluids. In particular, though this fluid is quite expensive, it’s one of the famous brake fluids in the market.

Motul 660 Wins

Now it’s time to discuss Motul 660 brake fluid benefits to know about it. Let’s discuss.

Motul 660 Wins
Overall Rating
  • Ultimate Thermal Resistance and Stability:

Under racing conditions, Motul 660 brake fluid gives high performance. In very high temperatures, it can fulfill the requirements of braking systems. Ergo, to generate the overall performance, it delivers outstanding thermal resistance and durability. In fact, it can help you make an effective brake in extreme conditions.

  • Efficient While Rainy:

From high wet boiling point to regular Dot 5.1, the non-silicone base fluid helps to keep breaking during rain. Always brake fluids can absorb dampness from the air. Furthermore, it can decrease the boiling point and enhance locking vapor risk.

Consequently, it measures a wet boiling point by humidifying with 3.5 percent water. Nevertheless, both features can minimize the air vents’ lower dry boiling point and slightly higher damp boiling point.

  • Resist To Extreme Temperature:

Motul RBF 660 is a 100% synthetic brake fluid. You can use this brake fluid in all types of hydraulic clutch and brake where you determine the non-silicone fluid. Besides, Motul dot-4 100 percent synthetic racing brake fluid especially comes to resist extreme temperatures. Plus, you can use these fluids with regular clutch systems and steel rotors if you want.

Motul 660 Losses

Don’t mix this brake fluid with Polyglycol based fluids that provide lower performance. If you combine this product, you can pay for this mistake. Still, avoid mixing this product with mineral-based brake fluids and silicone. They can lower the Motul 660 fluids quality and power.

Final Verdict

Regarding the Castrol SRF vs. Motul 660 combate, we have tried to give accurate information about them. Above all, you have to make the best decision. We hope you can make a good decision after reading this content. Overall, Castrol SRF and Motul RBF 660 fluids are best and ready to give the best performance.

Undoubtedly, after reading so many reviews, we will be glad to say that Castrol SRF is the best fluid and winner. However, this fluid is quite expensive but is an extraordinary fluid and provides excellent performance in extreme conditions. So, to get the best performance choosing this fluid is a great idea.