(Image/Gunk’s YouTube Channel)

Ever worked on your vehicle’s brakes? Then you’ve probably* noticed the characters “DOT 3” or “DOT 4” stamped somewhere on the brake system’s master cylinder cover. Those designations refer to the type of brake fluid that the manufacturer specs out for that particular system.

* There are more types of brake fluid than DOT 3 or DOT 4 (namely the silicone-based DOT 5/5.1), but DOT 3 and 4 are the most common, by far.

And it’s really, really important to know which kind of brake fluid to use, as the wrong type may impair the brake system’s performance.

To help explain why, we came across this 101-style video from the cleaning crew over at Gunk. In 60 seconds, you’ll get a great explanation on the differences between DOT 3 and DOT 4 brake fluid and, perhaps more importantly, in what scenarios they may be compatible.

If you’re unclear on the distinction between these two common types of brake fluid, give this video a watch, and you’ll know for sure after a minute.

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