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My owner's manual calls for DOT 4, what is the difference between fluids? Can I use DOT 34? I've read that DOT 5 is synthetic silicone, wouldn't this be best?
 

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You can use DOT "3and4" or DOT 4. You should be able to find it at any parts store. Don't use DOT 5, ever. It's not designed for the VW. A quick google showed this:




DOT 3 brake fluids are mixtures of glycols and glycol ethers. DOT 4 contains borate esters in addition to what is contained in DOT 3. DOT 5 is silicone chemistry

DOT 4 glycol based fluid has a higher boiling point (446F) than DOT 3 (401F), and both fluids will exhibit a reduced boiling point as water content increases. DOT 5 in its pure state offers a higher boiling point (500F) however if water got into the system, and a big globule found its way into a caliper, the water would start to boil at 212F causing a vapor lock condition [possible brake failure].
 

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Get a pressure bleeder or a mity-vac to bleed the brakes - it'll make it go much faster. Also don't use old brake fluid because it absorbs moisture out of the air. I know that if dot /4 brake fluid gets on the paint, it'll strip it so make sure to wash and wipe down any drips.
 

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On my previous Skoda 1.8T 20V, I raised the bar somewhat by using DOT 5.1 !
This quality is still Glycos, but with higher bolingpoint, the most noteable change was the Speed that the ABS-system worked with. Much higher frequency !
Although the best improvement was when re-newing the rubber brake-hoses to Airline-qual steel-bredded !
Funny thing is that they came cheaper than OE's ! and they were made by the factory that makes Yamaha bike breakes for the GP factory team ! ISR in Sweden (y)
 

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There is a bit of confusion over DOT5 fluid and its use

As mentioned DOT5 is silicon based and is not compatible with any other fluid DO NOT USE IN YOUR VW/AUDI!

Also mentioned is DOT5.1 which is a new high performance fluid but it is based on the same chemistry as the DOT3 and 4 fluids used on most cars and is entirely compatible with them so can be used for re-fills and top ups

I have a can ready for a drain and re-fill in the next few weeks when I do my next service
 

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If Your hesitant of what quality to use : http://www.valvolineeurope.com/english/products/brake__45__clutch_fluids/cid(555)/brake_/_clutch_fluid_dot_5_70_1

or even: http://en.wikipedia.org/wiki/Brake_fluid

I have tried DOT 6.0 , but this is over-kill and needs more pedal-Power . It's often used in TouringCarChampionship Racing together with High-performance Brakes.

It's quite common that carefull owners change the Fluid min every 2 Years, but how common is it to change the rubber breakhoses ?
Have a friend push down the breakpedal HARD, while You're holding the hose with Thumb and Indexfinger. If the hose seems to expand ? Change !
 
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