i need to oile my older machines i only use sweing machine oile now but i have always had a can of wd40 arround the house it works great on door latches when they just don't want to work or sticky car door latches and other things that move and just need a bit of oil but donot use wd40 on a brother sewing machine old or new most of those machine have plastic parts and wd40 will melt the parts i wound up throwing my brother in the trash because of this it was cheaper to purchase a new machine than to get my brother repaired some off us learnleasons the hard way
sewing machine oile can also help when trying to go through velcro and heaver fabricks just put some in your hand and smear it on your needle as this oil dose not stain material

I wonder if it's mineral oil?

a lady I know who works on older machines, treadles, handcranks, and older electrics says to never use wd-40. Instead use Liquid Wrench. Wd-40 will eventually leave a sticky coating she says. LW has kerosene in it and doesn't leave a coating. If a machine is really locked up and is all metal she'll soak the whole thing in a tub of kerosene. of course I've also read somewhere to never oil a machine with plastic parts in it period...that the oil deteriorates the plastic.

just did some checking yes sewing machine oil is mineral oil

tath is good for older machines but kersone will eat plastic parts on new machines a friend told me the way to tell if you can use and oil on somthing with plastic parts is put a small peice of plastic like from a milk jug in it over night if it becomes stick or melts donot use it on new machines i do like liquid rench better and you are right it is not good for some things i also have a cleaning spry for shuch things it is used to loseten stuch bolts i used it when i need to replace the light bulb on my out side light the screws were stuck tight and i used it and about ten minuets later i used my fingers to un skrew the skrews my dad is my sorce of info on a lot of stuff i rember back when my parents i though new nothing now they are one of my best sorces of info i feel luck to still have them arround at my age THANK GOD FOR PARENTS

There are different grades of mineral oil. Sewing machine is an extremly fine grade.

I only use the oil made for sewing machines.