WD40 has some oil in it but it is a water dispersant. It should be better than baby oil. I've been using White Lightening lately on my bike chain. The chain stays pretty clean but the lube doesn't last long. I guess any lube stickly enough to stay on your chain is also sticky enough for dirt to stick to.
One of the things I tried in skate bearings is engine assembly grease.because this was the lightest grease I could find. It was fast but lasted much longer than oil. For most skaters good old Lubriplate lithium grease is fine. It isn't as fast as oil but it stays put and lasts a long time. This is assuming that your bearings are high enough quality to have removeable seals for repacking.
A friend of mine uses WD40 on his bearings. I use the same on my bike chain and It's perfect. It keeps water out effectively, and it's nice and light for speed... cheap tooGood songs for a cheerleading dance?
No, baby oil is not a good lube for skateboard bearings. People trying to get every last bit of speed sometimes use light oils but sewing machine oil is better than baby oil. If you use a light oil you will probably need to relube every day but you will have the fastest possible bearings, at least as long as they last.
no it is not it will cause your bearings to rust and come out of socket