[nkaminar]

Different solders have different ratios of the components, normally lead and tin. The ratios determine if the solder melts all together or has a slushy stage where it can be worked like putty. I don't know the ratios for body solder, called body lead, but it has a slushy stage during heating. The body lead was worked with a wood paddle. The steel was tinned with a steel wool that was saturated with a tin compound. I don't know the chemistry of the compound but it put a bright tin on the steel so that the body lead could stick. The solder used for joining wires has a ratio of components so that it all melts at a certain temperature and does not have a slushy stage. It is called eutectic solder. It is not a good choice for filling in voids such as on the oil pan in question.

I hope there is an old body man (or woman) out there who can add some information to this.