steveproracing: I know maybe they dont have anything better when traveling but it but it doenst help
. Brake cleaner is good for new parts like diff balls or rings and outdrives though. New parts are often covered with some (non silicone) oil.
You can do the test with some a old shock oil bottle and spray some brake cleaner in... it will just not mix. Than use some isopropyl and you will see that it mixes immediatly.
Danny Harrison: WD40 is great for anything that mustn't rust and reduces friction much better than any silicone oil (which is very good to prevent rust too) I dont use it much but there are not many situations where WD40 is wrong. Basicly WD40 is for cleaning.