I'll always laugh at the guy who brought his dead gun to me because he kept spraying WD40 down his barrel!!!
AAHHH!! My eyes!! *cringes*
The only oils i use 100% silicone spray (CA is pretty good), lithium grease for the gears and other internals, and 3 in 1 and put in on a piece of cloth and rub it on the external steel parts such as the outside of the body pins to prevent rust.