I use it direct feed on all my cars (not yet on the 280CE though). On my wife's wagon and my SS (and all other b-bodies I've owned) I pull off the vacuum line to the brake booster (as it's the exact outside diameter of the bottle opening. 1/3 can? Nah, I use the whole thing and smoke out the neighborhood! I've only done it once per engine/car though.

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-James

'85 280GE...sold
'96 Impala SS ~ 6-speed 396
'14 Cadillac Vagon. . . . . . . . . . "Life without knowledge is death in disguise." - Hans-Peter Geerdes