DOT-3 & DOT-4

[David1]

Well Im not sure if this is possible or if its just me. Last time I did my brakes I flushed out all the Brake Fluid that was in the brake lines and put AAP house brand Wearever DOT-3 ..

Well I saw PRESTONE DOT-4 here is pic

on sale and decided to get it and I flushed out all the DOT-3 and put in DOT-4. Well I let my 02 Honda Accord LX V6 3.0 sit over night and this morning I drove it and when I hit the brakes I felt a difference like more stopping power. It felt like I didn't have to hit the brakes as much.. I mean the first stop sorta threw me up a lil...

Now I'm not sure if that is possible or what.

DOES DOT-4 do that?

I mean what are the benefits other then the DRY and WET Boiling point?

also is it possible to feel the difference as I think I felt?

Thanks

 

[Cardenio327]

You probably just had some tiny air bubbles that you flushed out when you bled the brakes this time. There shouldn't be enough of a difference in their hydraulic characteristics to notice when driving. If you had replaced DOT 3 or 4 with DOT 5 you would notice, I think I heard that 5 is slightly compressible while 3 & 4 are not.

The biggest obvious difference other than boiling temperature is that DOT 4 is required to be changed every 2 years while DOT 3 is recommended to be changed every 3 years.

 

[dnewton3]

The only real performance differences would come in that range between the points that DOT 3 would be compromised and DOT 4 would still be in an acceptable state.

Given than you were driving moderately, and then braked just a few times, it is unreasonable to think that the DOT 3 was too hot where the DOT 4 would be OK at the boiling point.

Much more liklye are three things:
1) it's subjective and you "think" it is "better"
2) you purged air that was previously effecting the DOT 3
3) some combination of these together

 

[Ken2]

Keep in mind that DOT3 brake fluid is polyglycol ether. DOT4 adds some borate ester to this to achieve the higher wet boiling temperature. In some brake systems there are elastomers that may not be compatible with the chemical difference. It is best to follow the recommendation for the original fluid. Usually not a problem, but sometimes....

I laugh at the "synthetic" on the label. Someone find me some natural polyglycol ether! I've had a helpful, well meaning parts store clerk even confirm with me whether I really wanted the synthetic product.

 

[brandini]

Originally Posted By: Ken2
Keep in mind that DOT3 brake fluid is polyglycol ether. DOT4 adds some borate ester to this to achieve the higher wet boiling temperature. In some brake systems there are elastomers that may not be compatible with the chemical difference. It is best to follow the recommendation for the original fluid. Usually not a problem, but sometimes....

Short version: seal compatibility, you are risking it on your braking system.

 

[stchman]

The only difference between DOT-3 and DOT-4 is boiling point. DOT-4 does not give a better feel to the brake pedal.

The OP either had some air bubbles in his brake lines or the placebo effect kicked in. I am going to change the brake fluid out on my truck soon and will use DOT-4 as the price difference between DOT-3 and DOT-4 is minimal, and if I tow some heavy loads the extra heat capability of DOT-4 won't hurt, but I don't expect the brakes to feel different.

 

[HTSS_TR]

I switched DOT-3 and DOT-4 in my LS400 and E430 several times in the past and could not feel any difference. Now I use only DOT-3 and bleed the brake every 3-4 years in all my cars.

Even after 4 years the fluid came out barely darker than new fluid, the brake feel with new fluid was the same as old fluid.

 

[jake88]

The main difference is wet boiling point - for a freshly flushed fluid there is really not any difference. Likely just a subjective feeling or result of getting some air out during your bleed.

There are some very high performing DOT 3 fluids with dry boiling points north of 480F. The wet boiling points are the big difference, as water causes the borate ester to hydrolyze - it chemically reacts with the water so that there is not as much "free" water affecting the boiling properties.

 

[David1]

So do you think I should go to HONDA and get the OEM Heavy DUTY DOT 3 ???

Someone said the DOT 4 can possibly hurt the system ???

THanks

 

[David1]

Originally Posted By: David1
So do you think I should go to HONDA and get the OEM Heavy DUTY DOT 3 ???

Someone said the DOT 4 can possibly hurt the system ???

THanks



EDIT

Going to dealer and get OEM HONDA HEAVY DUTY DOT 3

 

[David1]

LOL

it says on the brake Fluid CAP on my car.

Use DOT-3 or DOT-4 ONLY from a sealed Container.

So I would think DOT-4 would be Okay?

Correct?

 

[David1]

Originally Posted By: David1
LOL

it says on the brake Fluid CAP on my car.

Use DOT-3 or DOT-4 ONLY from a sealed Container.

So I would think DOT-4 would be Okay?

Correct?



Well since I had the OEM HONDA Heavy Duty DOT 3, However I fail to see anyplace on the bottle that says the words Heavy DUTY... Anways since I bought the bottles I just went ahead and bleeded the DOT4 out and put HONDA DOT3 In.

Thank for all your INPUT

However I asked the guy at the dealer, I told him that I put DOT4 in and he said it could damage the brake LINES.

However if that is TRUE How come the CAP says DOT 3 or DOT 4 Only ??

Strange

 

[tommygunn]

Any reputable DOT 4 (name brand, or well-known chain's house brand) should be fine. They usually test them for compatibility.

Some of them, such as Valvoline brake fluid, are even labeled "DOT 3 and 4"

 

[andyd]

DOT 5 is the incompatible brake fluid. Only difference betwixt 3 and 4 is wet boiling point. You must be great at bleeding brakes by now.

 

[GutsyGecko]

ALL dot 3 and 4 are compatible. 5.1 is also compatible. It will not harm a thing. It's actually beneficial to use a dot 4 as it has higher boiling points.

 

[dailydriver]

Originally Posted By: jake88
There are some very high performing DOT 3 fluids with dry boiling points north of 480F. The wet boiling points are the big difference, as water causes the borate ester to hydrolyze - it chemically reacts with the water so that there is not as much "free" water affecting the boiling properties.


What I have noticed about those very high DRY boiling point DOT 3s is that they sometimes have a LOWER WET boiling point than the standard, 'low performance' DOT 3s, let alone the standard DOT 4s (like the Motorcraft DOT 3, as an example).

I wish someone would make an affordable ultra high WET boiling point DOT 4/borate ester fluid, at Castrol React SRF's level of WET BP, but without the 'Bill Gates ONLY' price tag.

 

[wander2039]

And nobody asked mileage since the last flush? Most likely the only difference you felt was the new vs old. Flushed the Focus out recently from factory DOT3 to DOT3.. after 114k even with brake booster flushes it was needed. It's like a new car stopping wise.

 

[David1]

Originally Posted By: Eric Smith
And nobody asked mileage since the last flush? Most likely the only difference you felt was the new vs old. Flushed the Focus out recently from factory DOT3 to DOT3.. after 114k even with brake booster flushes it was needed. It's like a new car stopping wise.


Have you read about Castrol LMA ??

Im told that is awesome DOT3 / DOT4

can be used in DOT3 or DOT4 systems.

The other day I blew out all the old Brake Fluid in my Honda and put in Preston DOT4 and it felt like my brakes woere stronger and people here told me it was probably b.c the old fluid had water and air in it...

And they said to take the DOT4 out b.c it can harm the system.

Soooooooo

I went to the Dealer and bought HONDA Genuine DOT3 brake Fluid and Bleed the system clean and then put in the Honda DOT3 and it felt nice and FIRM just like it did with DOT4

However I have read people who have MOTORCYCLES Say the Castrol DOT3/4 is awesome and there frinds can actually feel the difference.

 

[y_p_w]

I've got a couple of bottles of Federal-Mogul DOT 5.1. It wasn't super cheap, but maybe $5 for a 12 oz bottle. It no longer comes in metal cans, which some people really believed to help with shelf life. I've also got some older Motul DOT 5.1.

I'm still wondering what was the point of discarding perfectly fine DOT 4 brake fluid. In the long run the wet braking point is the most important thing for a street car. I understand that some racers use a heavy duty DOT 3 with a high dry boiling point and change it before each race, but brake fluid gets changed out every year - tops. Some manufacturers that don't even specify a brake fluid change period.

There's nothing special about what Honda sells as their brake fluid except maybe the price.

 

[artificialist]

I once felt lighter brake effort in a Saturn ION by replacing the OE fluid with Valvoline DOT4. I found no air in the system. The only reason I could imagine one fluid would require more pedal effort than another is if the viscosity is different.