My kid did a science project in high school some years back, testing various products under lab controlled rusting tests. ATF came out best. You guessed it, WD40 failed in the first few hours. That was before synthetics though, and I hear nothing but good about Mobil 1.
A machinist torqued bolts to a steel plate.......sprayed with salt water till well rusted.
Checked all the different penetration oils and sprays ........lowest torque to remove was 1/2 ATF and 1/2 acetone........next was about twice as much to remove.
