I have an alloy wheel which is rusted onto the drum. I have watched dozens of YouTube videos regarding making your own (more effective and less costly) penetrating fluid. I am very concerned, however, with damaging my alloy wheel. One of the primary ingredients most recommend is Acetone - and I have seen references to various forms of alcohol (both "food grade" and toxic). I am not a chemist, so are there any suggestions? I would like to stay with DIY as I have other uses for such fluid.
May I suggest a Big Hammer?
Usually, alloy wheels separate from the drum just by using a hammer. I'm not sure about your situation, but the hammer trick has worked for me always. This is for cars that have been used regularly and the wheels have been changed regularly (I live in an area where using winter tires is mandatory during the winter).
I suggest using a hammer made from a soft material such as plastic or rubber, because metal hammers may damage the wheel if you hit the wheel hard.
Edit: Solar Mike correctly observed that hitting the tire sidewall with a hammer is a better option instead of hitting the rim. I have no reason to doubt his expertise, and when hitting the sidewall, you can use any hammer, no reason to limit yourself to non-metallic hammers.
I'm not so certain about the penetrating fluid. There is usually some oil in it, and you don't want oil near your brake parts.
There are other tricks as well: loosen the lug nuts slightly (DON'T REMOVE THEM!) and drive hard for an extremely short distance, accelerating and braking. I'm not comfortable with these other tricks, however, so I continue to use a hammer.
From the chemical side, acetone, oils, alcohols and other solvents do not interact with metals under normal conditions. But some can dilute paint, which is especially true for acetone and cellulose thinner. Alcohols and benzine are usually safe on a car.