Many people swear by DOT 3/4 or DOT5.  Others swear at DOT 3/4 or DOT5.

Army Jill in the 1942 Ford GPW

DOT 3 and 4 are designed to absorb moisture so when moisture get into your brakes (and it will because it is open to the atmosphere.) Sure it requires changing frequently. I change my brake fluid about once a year…unless I have been driving through water then I change it again. It is an inexpensive product.

Now on the flipside, DOT5 will not absorb water, so pockets of moisture can form and lead to erosion/damage, too, perhaps moreso. However, if you change it out once a year you might be okay. Another potential problem with DOT5 is that it contains dissolved air which is released when the DOT5 is heated. How hot can you brakes get with a jeep right? That’s what I would think, too. However, you will recall that your master cylinder is sitting awfully close to the heat exhaust. Do you have the shield in place? How effective is it? I had one in place. When I used silicone, my brakes were always spongy. I could never get them to bleed out properly (to a point that they were no longer spongy).

Never mix the two.

The problem with DOT 5 is that some people substitute it for proper maintenance. If all you do is push your jeep on to a trailer and off a trailer for a jeep show then sure use DOT 5.

The jeep is antique equipment and open to the atmosphere. DOT5 doesn’t absorb moisture there in lies one of it’s more serious negatives. The other serious negatives are air dissolved in the fluid and bubbles in the fluid that are a PITA to get rid of. I tried DOT5 when I redid my brakes (before going on to disk brake….the horror) and they were mushy (after bleeding numerous times and detecting no pressure loss or leaks. Another negative is condensation which happens with temperature and air pressure changes. The moisture will sink to the lowest level and be pushed into your wheel cylinders.

Of course that’s not necessarily a bad thing as long as you recognize the issue and periodically flush.

A “plus” is supposed to be it won’t eat paint? I dunno that sounds like a big whoop to me. I have never spilled DOT 4 or 5 on my jeep.  So is this a smoke screen?

Well, this subject is a lot like others were you are aren’t likely to make many converts.

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