While checking the oil this morning, I noticed a little oily residue on the hose coming from the power steering reservoir. I don't yet know if it's a minor leak or just some sloppiness left over from the last fluid change. I have some brake cleaner handy ... can I use it to clean the oily area on the plastic reservoir and hoses ... will the cleaner cause any damage?
For rubbers I usually check "rubber compatibility" charts, there's a good one here: https://www.minorrubber.com/compatibility-chart.html
Brake cleaner is usually perchloroethylene or tetrachloroethylene, both of which has mostly unsatisfactory ratings against most rubbers, especially the kind they use under the hood these days which is EPDM. That said
, I've used brake cleaner on lots of rubber brake parts, boots and the like and hoses too without ever having an issue, plastics too. If the engine bay is hot or you do it in direct sunlight it's going to speed up the chemical reaction so that provides more opportunity for "damage" in the same timeframe cold. About the only thing I don't use it on is painted and powder coated surfaces like the subframe, it tends to soften and dull those (but you can usually make them shiny again using another solvent mixed with oil, like WD-40).
70% isopropyl alcohol put in a $1.50 spray bottle from Walmart also cuts oil residues extremely effectively without leaving any residue, (as long as you get one that isn't green with added mint scents or whatever) and is far less harsh if you're worried about that. On the chemical resistance chart it has A ratings on nearly every type of rubber.
If you're concerned do it when the engine is cold, use isopropyl or use the brake cleaner but spray it on a shop towel and do brisk passes over the surface, dousing it with brake cleaner and letting it run off is a waste anyway. I don't exactly know what test regimen they use for the compatibility chart, their ratings may be derived from the rubber being in constant long-term contact with the chemical (like a hose containing the chemical) which is different than brisk passes over a period of a minute...