As the parent of person fed by g-tube for medical reasons, there are lots of things that make my job easier! I feed blended meals using a 2 ounce (60cc) syringe. I do this four times a day. That means I wash a syringe four times a day. (I used to have 6 – 8 syringes and feeding tubes in use simultaneously so that I wouldn’t have to wash one right after using it. This was replaced by a NEW system because I hate washing 8 syringes and tubes at once! Plus, where to put them?? right? So now I have only 2 – 3 syringes and tubes in play at a time and I just wash them as soon as I’m done, mostly. That means they last longer and I can just store them on top of the dinner plates in my cabinet.)
Anyway, the thing about syringes is that they have a rubber tip on the end of the plunger. Rubber oxidizes over time. That means it is not as smooth and doesn’t glide (nor fit) as well in the syringe barrel as it does when brand new. The solution is lubricant. I use olive oil because I have a handy olive oil bottle with a nice pour spout that allows me to pour only a few drops on the rubber tip of the plunger. Also, olive oil does not turn rancid quickly so it is safe for me to use in this way.
However, if you want more assurance that you will avoid rancidity, you could use mineral oil. I hear that it is safe (in small quantities) internally – and will not turn rancid. If you put it in food though, you are making a mistake. It is a by-product of petroleum, so not really a food product. There is food grade mineral oil – which is commonly used for lubricating cutting boards, wooden knife handles, etc.