plastic rollers in a traveller
We have a Goiot traveller with plastic rollers about 3/4" diameter that run on stainless steel shafts about 3/8" diameter
What is best lubricant?
I would like to use 30 wt oil, thinking that it will not run out too easily, but am concerned that it may swell the (unknown, black) plastic rollers.

Vegetable oil would be safer in this respect, but would wash our more easily and is a less effective lubricant

If I use oil, I have light 3in1 oil, engine oil and hypoind gear oil. Which is best degree of fluidity?

I cannot take them off the shafts to use grease and have no teflon spray available

I have not been able to find any relevant wisdom on the Goiot site