This weekend I did a front brake job on my vehicle. After using 2 cans of commercial penetrating oil (lubricant) I still could not remove the rusted brake rotor from the axle spindle. I had tried various additional things like a bigger hammer, heat and rapid cool, it would not come off. Now this is not my idea, it took about 2 hours of internet browsing to find a solution and people who tried it were singing it's praises and now I am a believer also. One person on another site said there was actually a study comparing this home-made to commercial brands and the home-made required 30% of the torque of commercial brands to loosen rusted bolts. And it is by far cheaper than the commercial brands like WD-?? for example.
Here is what you need. A cheap spray bottle (you probably have an empty one laying around). In this bottle mix a 50/50 mix of 100% acetone and dextron/mercron automatic transmission fluid. The two fluids will separate like oil and vinegar so you have to shake the bottle well before spraying.
I mixed up a batch and let it soak for 15 minutes on the rotor and with a few taps it came right off. Yesterday I spent 6 hours with 2 cans of the commercial brand with no success. My other rotor was equally rusted, and came off the same with this stuff only.