This is for 4 Jaw Chuck, just wondering about you saying (never mix fluids of different DOT classifications). I know you can't put DOT3 into a DOT4 system because DOT4 is rated higher. It would be like putting type F trans fluid in a new car calling for MerconV. But I have a bottle of Castrol GTLMA brake fluid in front of me. It says right on it 'exceeds DOT3 and DOT4 specifications and mixes with both'. It's more expensive so we don't generally use it unless the system calls for DOT4 but sometimes if we're out of DOT3 at our station we'll use the DOT4 until we get more from parts dept. It says right on the bottle mixes with all conventional brake fluids (DOT3 & 4). Yes if you add DOT4 to DOT3 you are lowering the boiling point of the DOT4, but if the system only requires DOT3 you're still ahead of the game.
BUILT FORD TOUGH