The main active ingredient in WD 40 is 50% "aliphatic hydrocarbons".
WD 40 is a penetrating oil and water displacer which was introduced in the year September 23, 1953.
I use WD 40 all the time and would never be without it as it's a very safe and effective lubricant and water displacer to help prevent rust.
I also spray a bit of WD 40 in my lawn mowers gas tank to help displace water when the weather is more humid or damp outside.
It helps to keep the water droplets and moisture out of the gasoline tank in the lawn mower.
Another good product besides WD 40 for removing stuck bolts is some PB Blaster and I love that stuff when WD 40 won't do.