I hope y'all had a Merry Christmas.
Has anyone used DOT 5 (not DOT 5.1) silicone brake fluid? Any observations?
I am replacing the entire brake system in my truck so I don't have to worry about cross contamination. I picked up a bottle of the stuff and soaked a spot on a rattle can paint job for over a week and it had no effect at all.

 

the dot rating has to do with tempature ratings. i doubt your notice any difference between the 5 and 3. its still basically a hydrological flid used to transfer force from the pedal to the breaks. with a higher temp rating.

 

Here's a linky to a Summit Racing customer help page.

https://summitracing.custhelp.com/app/answers/detail/a_id/414/~/dot3,-dot4,-dot-5-and-dot-5.1-brake-fluids

Quote from linky...
"What is the difference between DOT 3, DOT 4, DOT 5, and DOT 5.1 brake fluids? DOT 3, DOT 4, and DOT 5.1 brake fluids are glycol-based compounds that are compatible with one another. On the other hand, DOT 5 brake fluid is silicone-based and should never be mixed with any other type of brake fluid. DOT 3, DOT 4, and DOT 5.1 brake fluids will damage painted surfaces. DOT 3 and DOT 4 fluids have lower boiling temperatures than DOT 5 and DOT 5.1. Furthermore, DOT 3, DOT 4, and DOT 5.1 fluids are hygroscopic--they absorb moisture from the air. This causes the fluid to turn dark, indicating that it is time for the brake fluid to be replaced. DOT 5 fluid will not damage paint, has a boiling temperature in excess of 500 degrees F, and is not hygroscopic."

 

Personally, I think this is the best part about it.

 

That should help if you live in a humid climate.

 

Wow...

 

I would add that DOT5 will function properly if mixed with DOT 3/4. By law, brake fluid must be miscible and is tested mixed together before approval. If you switch to DOT5 and there is a little 3/4 left in the system, no big deal.

 

I know I run dot 5 in my Harley and was told to never mix anything in but 5

 

the point i was trying to make is you wont feel in difference in the pedal on the type of fluid your using. it will work the same. these are not high performance race cars where your going to boil the fluid even with dot-3. if the other benefits of the fluid suit you then go for it but you wont notice any difference in pedal feel or break performance.

 

Best practice is to not mix your brake fluid. Yes if you're trying to get out of the desert then mix away. The OP's system is empty and clean.

I ran DOT 5 silicone before and The biggest issue I had was it is harder to find in stores.
Can't remember where I heard, but seems I recall it's ok to change from dot 3 or 4 to DOT 5 silicone with a good flushing. But once dot 5 silicone is in a system it is not recommended to go back. Something like it doesn't clean out well. Everything I've read or have been told, DO NOT MIX Silicone fluids with other types.

People will say the dot 5 lasts longer and does not turn dark so it doesn't need replacing. But stuff like moisture and wear debris still get in to the system so making it last longer doesn't make sense.

As mentioned conventional brake fluid absorbs moisture where as silicone will not and it will collect as water in the low parts of the system and cause rust. Silicone and water do not mix. So for this reason I'm going back to Dot 3 brake fluid on my current build. I can change fluid when the color darkens.

As for temp ranges between the DOT 3,4&5.1, as mentioned probably not an issue in an old truck. Race Track? Heavy Loads? Experience heat related pedal fade? Then maybe a good idea.

There is a lot of good information out there on the web from a lot smarter guys than me.

To 884x4's point, feel on the pedal is the same, at least at cooler temps.