A4 brake questions
 

Recently my brake warning light and alarm have been going off intermittently. I checked my brake fluid reservoir and the fluid level seems to be fine. Any ideas?

Also, Audi calls for the use of DOT 4 brake fluid in the A4's. But everywhere I looked I could only find DOT 3 fluid. What's the difference?

Some info....
 

<ul><li><a href="http://www.rpmnet.com/techart/fluid.shtml#fluid">http://www.rpmnet.com/techart/fluid.shtml#fluid</a</li></ul>

Some info......
 

<b>DOT 3 BRAKE FLUID</b>
Brake fluid that meets the Department of Transportation specifications for glycol based fluids with a wet boiling point (lowest allowable after it's been in use) of 284 degrees F. and a dry boiling point of 401 degrees F. DOT 3 fluid is the type commonly specified by most vehicle manufacturers. Because it is glycol based, it absorbs moisture over time (hygroscopic). This lowers its effective boiling point and promotes internal corrosion in the brake system. For this reason, the brake fluid should be replaced periodically (every two years is recommended by many experts) and every time the brakes are relined or serviced.

<b>DOT 4 BRAKE FLUID</b>
A "heavy-duty" glycol based brake fluid with a slightly higher wet boiling point of 311 degrees F. and a dry boiling point of 446 degrees. This type of fluid is sometimes specified for performance vehicles or those subject to high brake temperatures.

<b>DOT 5 BRAKE FLUID</b>
A silicone based fluid that does not absorb moisture and has a boiling point of at least 500 degrees F. DOT 5 fluid does not have to be changed periodically and can minimize brake system corrosion, but is very expensive compared to DOT 3 or DOT 4 fluid (it costs three to five times as much). It will not mix with DOT 3 or DOT 4 brake fluid. DOT 5 is NOT recommended for any vehicle with ABS brakes because it tends to aerate when cycled rapidly through small orifices.

Re: Some info....
 

Can I put DOT 3 fluid in my car even though the manual calls for DOT 4? Can the two fluids be mixed?

I'm not an expert, but I wouldn't....
 

...if you're really in a pinch and can't find it anywhere (hard for me to believe), your local Audi or VW dealer will have it.

I agree with Andy, don't mix. Go to your Audi Dealer and get a bottle.