Here's a Tech Article I wrote for PCA a few months ago ...

I have posted recently concerning my clutch dragging/not releasing completely. I just read another post concerning the use of DOT 4 fluid. I used DOT 5.1 I don't know the differences in the ratings. Is this possibly a cause?

This link should tell you all you need to know. I have to admit that I have always used Castrol LMA DOT 4 brake fluid even if the mfg called for DOT 3 and to date haven't had any issues. I do a flush every 2 years.

[www.stoptech.com]

... which should answer your questions.

[www.pedrosgarage.com]

Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Porsche specifies DOT 4 plus, and uses (reputedly) ate super 200 at the factory.

Grant

DOT 3,4, 4+ and 5.1 are all 100% compatible

DOT 5 (not 5.1) is silicone based and is not compatible. Also nto good with ABS.

Higher the number, higher the temperature (by and large).

For street cars i suggest Castrol GT-LMA. Cheap, good and absorbs less water. For track cars you will want something hgiher temp, btu must change it every year, or more.

Grant