Motul RBF 600 vs Motul RBF 660

Both Motul RBF 600 and Motul RBF 660 are entirely synthetic along with an identical visual appearance. On top of that these braking fluids are equally compatible with all types of cars as well as with motorbikes, and have similar safety standards.

RBF 600 is a DOT 4 brake fluid capable of exceeding DOT 3 standards. These fluids can be used for all kinds of braking systems except the one which uses silicon-based fluid. It has a quite high dry boiling point plus its wet boiling is also on the higher side. During chilly conditions, the performance of this fluid is also very impressive because of its high viscosity. The long intervals of replacement further make it a very attractive choice for the consumers.

RBF 660 just like its peer, is also a DOT 4 brake fluid. These fluids are designed to counter extreme high-temperature conditions as they possess very high boiling points. This fluid can also be utilized for traditional steel disc brakes along with hydraulic clutch actuators. As the oil exhibits a very high wet boiling point, it provides a much longer duration of exchanging compared to other brake fluids.

Comparison Table

SpecsMotul RBF 600Motul RBF 660
Oil typeWholly SyntheticWholly Synthetic
Automobile CompatibilityCars and bikesBikes and Cars
Article Number100948101666
SAE StandardJ1703J1703/ J1704
Safety StandardFMVSS 116 DOT 4FMVSS 116 DOT 4
ApplicationsBraking fluidBraking Fluid
Packaging500 ml500 ml
Price per half liter20 to 25 US Dollars30 to 35 US Dollars


These fluids are manufactured for cars and motorbikes irrespective of their model either old or latest. These braking fluids fulfill the requirements of all hydraulic actuated clutch as well as braking systems which needs fully synthetic fluid for their smooth functioning. They also come in with similar packaging and have identical safety standards. The visuals of these special liquids are also familiar with one another as both exhibit a similar amber color appearance.


The rating of oil is mentioned in the form of DOT which is an abbreviation for the Department of Transportation that has developed certain standards for depicting fluid composition. These are represented as DOT 3, 4, 5, and 5.1. Except for DOT 5, all the remaining standards are made up of glycol and can be mixed with one other for further enhancement in performance. The DOT 5 fluid contains silicone as its primary constituent and it cannot be assorted with any other fluid which comprises glycol.

In this case, both fluids are rated as DOT 4 indicating that they are manufactured from glycol and can be mixed up with other fluids for increment in their performance. However, 600 leads the race with the slightest margin as it is designed in such a way that it exceeds the DOT 3 and DOT 5.1 standards without any mixing as compared to its counterpart.

Boiling Temperature

Two types of boiling temperature portray the behavior of braking fluids including dry boiling point and wet boiling point. The dry boiling point is the temperature that the fluid will achieve without absorbing any water vapors. As the fluid is added to the system, moisture gets incorporated after some time. The boiling point the fluid finally achieved after the mix-up of moisture is referred to as the wet boiling point. The higher this wet boiling point the higher will be the longevity of the oil and vice versa.

660 performance is ahead of its counterpart when the fluid is still new that is when no water vapors entered it as it has a greater dry boiling point in comparison. Conversely, 600 will reach its boiling point sooner even when no moisture is present.

As the moisture becomes part of the fluid with the passage of time, its boiling point drops compared to the dry boiling point. In this case, both the fluids have similar wet boiling points illustrating their equal compatibility in this regard. But overall, 660 is ahead of its rival.

Contrasting brake fluidsDry Boiling Temperature (o C)Wet Boiling Point (o C)
Motul RBF 600312205
Motul RBF 660325205

Viscosity Comparison

Viscosity represents the thickness of the fluid. It is very essential when it comes to brake fluids as it regulates safety as well as influences the behavior of the braking system. The viscosity of braking fluids is mentioned for extremely low temperatures (-40 o C) and for high temperatures (100 o C). If the fluid has higher viscosity at these foregoing temperatures, it would perform much better than the reverse scenario.

600 has higher viscosity comparatively at -40 o C which makes it cut above its peer. Therefore, it will perform more dominantly during such conditions. 660, which has lower viscosity in frosty conditions, will perform superiorly because of its greater viscosity at elevated temperatures that is at 100 o C. So, the performance of 600 is better in colder conditions meanwhile 660 will perform much better during higher temperatures.

Contrasting brake fluidsViscosity at -40 o C (mm2/s)Viscosity at 100 o C (mm2/s)
Motul RBF 60017502.5
Motul RBF 66016982.6

Fluid Replacement Interval

The addition of moisture in the braking fluid after a passage of time causes it to be interchanged after specific intervals. The higher the addition of moisture, the sooner the fluid is needed to be replaced. The fluid which has a higher wet boiling point would be more effective and require to be changed after longer durations and vice versa.

Both the clutch fluids have identical wet boiling points. The similar boiling points cause them to be exchanged after equal intervals of time. The maximum duration of their working is almost 12 months after which they should be interchanged to ensure smooth working of the braking system.

Cost Differentiation

In terms of cost, RBF 600 is inexpensive making it more budget-friendly. The half-liter price of this brake fluid is between 20 to 25 US Dollars. The reasonably good performance specifically during freezing situations makes this fluid one of the best in the business. On the other hand, RBF 660 is pretty extravagant as compared to its peer. The cost of this clutch fluid falls in the range of 25 to 30 US Dollars for each half-liter bottle. The higher boiling point, as well as viscosity at elevated temperatures, somewhat reimburse this expensive price.

Quick Summary

  • These brake fluids are entirely synthetic.
  • Both of them are equally compatible with all types of cars and motorbike models.
  • These are both DOT 4 fluids however the overall effectiveness of 600 is marginally better than its rival.
  • 660 has a higher dry boiling point however the wet boiling point of both these fluids is identical.
  • 600 possesses a higher viscosity in frosty conditions meanwhile 660 exhibits greater viscosity during high temperatures.
  • The duration of the replacement of these clutch liquids is similar.
  • The price of 660 is much cheaper as compared to its peer.