What's new
Van's Air Force

The definitive Van's Aircraft support community! Buying, building or flying an RV? Join our exclusive family of mentors and enthusiasts!

Break Fluid Lower Cost Options

F

Frankster13

Well Known Member
I was told that there are reasonably priced substitutes for expensive break fluid at local auto parts stores. I was told certain red, synthetic automatic transmission fluids are a viable substitute. Anyone know the chemistry?
 
Any light weight/low viscosity fluid will work fine ( even water other then freezing and corrosion issues) Don’t use water just making the point that it will work as a hydraulic fluid.
Most any automatic transmission fluid or light machine oil regardless of color will work given it’s in the correct viscosity range for the system ( smaller lines require lighter weight/thinner viscosity) to have proper flow reaction characteristics.
Main concern with using non standard items is compatibility with other materials and existing fluid that are in the system, without knowing what all the little rubber and plastic bits “O”rings and seals are made of and compatible with. The wrong fluid might turn them into gummy wads of gunk, which would ruin your whole day.
 
You'll need such a small quantity that experimenting with another option seems out of line with the benefit of lower cost.
There are many better and more efficient ways to save money.
If however, you want to do this simply to experiment with a locally available replacement, I would take Walt's suggestion.
 
I used Mobil 1 ATF and is working well at 1 year. Many others use it. BTW, it's my lube of choice for the shop oil can for misc lubrication.
 
Frankster13 said:
I was told that there are reasonably priced substitutes for expensive break fluid at local auto parts stores. I was told certain red, synthetic automatic transmission fluids are a viable substitute. Anyone know the chemistry?
Click to expand...
Don't use any automotive brake fluid unless your aircraft brake system says to use it specifically.
 
I've been using ATF in Matco brakes for more than 12 years. No problems. The other advantage is it is locally available if you need it.
 
Last edited:
RNB said:
Were you into certified or experimental aviation first?
Click to expand...
Certified, however I like to think I still follow accepted best practices even in EAB.
Using aviation approved products is a big reason I built an RV; I prefer Lycoming and Hartzell up front.
Saving a few dollars is never my goal. If it was, I'd find another hobby!
 
Compatibility: Long ago I was a shop rat for a Piper dealer. One of the base customers with a Cherokee 6 was on a trip and added some auto brake fluid. He made it home barely, but the aviation grade MS “O” rings were softened/melted. As the new guy I was given the fun job to replace every “O” ring in the brake system which on a Cherokee is easily a couple days. Don’t remember if we considered if the flex hoses may have been damaged? This was before hoses with Teflon lining. Proceed with Care & Caution.

Don Broussard
RV9 Rebuild mostly done
57 Pacer
 
Frankster13 said:
I was told that there are reasonably priced substitutes for expensive break fluid at local auto parts stores. I was told certain red, synthetic automatic transmission fluids are a viable substitute. Anyone know the chemistry?
Click to expand...
Buy and use the proper brake fluid. Once filled you will hardly ever have to use it again unless you develop a leak. Trying to save a very few dollars on a plane worth possibly a $100,000 plus is not worth it. Also if you are using some unknown cheap brand X what are you going to refill the system with if you develop a small leak that can't be repaired out in the boonies when all the locals only have the proper stuff, mixing is most often not acceptable.
 
I use ATF not for savings, but increased performance. Atf by its nature is a hydraulic fluid, so a good fit in braking systems, which are hydraulic systems. The also contain excellent seal conditioning additives to help the o rings last longer. Finally it has a flash point much higher than the original aviation standard fluid. In my experience, many aviation standards are seriously outdated and don’t follow them. Far from universal, as many of those standards offer higher quality and reliability. Many of the standards just haven’t changed to keep up with improvements.
 
lr172 said:
I use ATF not for savings, but increased performance. Atf by its nature is a hydraulic fluid, so a good fit in braking systems, which are hydraulic systems. The also contain excellent seal conditioning additives to help the o rings last longer. Finally it has a flash point much higher than the original aviation standard fluid. In my experience, many aviation standards are seriously outdated and don’t follow them. Far from universal, as many of those standards offer higher quality and reliability. Many of the standards just haven’t changed to keep up with improvements.
Click to expand...
What's the flash point compared to Royco 782?
 
Walt said:
What's the flash point compared to Royco 782?
Click to expand...
I believe they are pretty close, but thought the atf was a bit higher. My post was referring to the old stuff, where there is a significant difference and it is still an aviation product. My primary reason for atf is the seal conditioners. I have seen transmissions that go on for decades and 100’s of 1000’s of miles on original orings and rubber seals. The stuff truly works.

To be clear, i am not against using aviation standards. I just don’t believe 100% of aviation standard products are the best out there. Though i believe most are.
 
Last edited:
Royco 782 Flash Point 445*F (Aircraft Spruce Product Data Sheet)
Mobil 1 Synthetic ATF 428 deg F (220 deg C) (Mobil 1 Product Data Sheet)
 
Automatic transmission fluid is fine. I like the synthetic blend, very heat tolerant and it looks like 5606 for the nosey lookers
 
lr172 said:
I use ATF not for savings, but increased performance. Atf by its nature is a hydraulic fluid, so a good fit in braking systems, which are hydraulic systems. The also contain excellent seal conditioning additives to help the o rings last longer. Finally it has a flash point much higher than the original aviation standard fluid. In my experience, many aviation standards are seriously outdated and don’t follow them. Far from universal, as many of those standards offer higher quality and reliability. Many of the standards just haven’t changed to keep up with improvements.
Click to expand...
I am on board and agree with Ir172 here, Years ago I did a bunch of research on flash point of hydraulic fluids and Toyota ATF was the highest and that is what I use and it definably is not because of the cost.
But my luck varies FIXIT
 
Another happy Mobil 1 ATF user, here, in both experimental and certified. Try to find aviation brake fluid in BFE. You also can't fly commercial with brake fluid anywhere in your baggage.
 
You must log in or register to reply here.
Back
Top