mineral oil is what magura,s are blead with so don't bother butting any other substance in them. dot fluid is an oil based substance which hopes are bled with. Whoever bleeds his brakes tell him not to put dot 4 or 5.1 anywhere near maguras cos it will just f**k the seals. and these can't be replaced. sounds to me that every time he keeps rebleeding it air has got into the system so get a bike shop to bleed them or some one who knows what there talking about . Just tell him to get a new brake because re-reading the topic it sounds like the seals are knackered.] O and yes baby oil is a cheap solution rather than magura blood and it works fine. But i've always bled mine with water and nothing as ever happened to them.