GL4 vs. GL5

Louis-Alain Richard larichard at
Wed Dec 11 15:55:22 EST 2002


If you can find some, Castrol Hypoy IS really mineral GL4 oil.  However, my parts store carry only Castrol Hypoy C, which is GL5.  And like you, I did it last summer with the wrong one so I want to switch back to GL4.

Interestingly, the oil I drained form the car was Dexron ATF (thin, red slippery stuff) like you find in any manual trans GM car!  Somebody probably wanted to ease the gear change and they were right; the trans was really easy but longevity was my primary concern.

Try this link: <>

83 urQ

Subject: GL4 vs. GL5
From: qshipaz at

Greetings Audinauts,
Hmmm. I heard that GL5 should not be used, but could never remember why. Guess the GL5 I topped the TQ box off with last week is gonna come out! Question, though: I believe in Redline's quality, but I am superstitious about using synthetic in a car which has likely always used "bean oil"- maybe just for the potential of new leaks developing. But otherwise- where can you get non-synth GL4?? I used to use Castrol in my departed 5kt, but I can't locate the stuff anywhere....


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