Originally Posted by
Stanwell
If I may add to onetrack's response, the major component of WD-40 is kerosene (paraffin, to those in UK).
I'd looked up the safety data sheet for WD-40 a while back, by weight it's >60% naphtha (petroleum), hydrodesulfurized heavy (CAS #64742-82-1). Naphtha has basically the same flash point (47 °C) and upper/lower flammability limits (1. 4 - 7. 6 % (V)) as petrol (motor spirit, gasoline).