Is it possible to mix vegetable oil with kerosene? If not, what other solvents can be used to reduce the viscosity of cooking oil/vegetable oil.
Cooking oil and kerosene will mix well, just do not cook with it afterwards !
It is important to keep in mind that there is no such thing as a "standard kerosene". I tend to use two different kerosenes for solvent extraction, I like the solvent 70 which is aliphatic kerosene and solvesso150 which is an aromatic kerosene.
You can regard an aliphatic kerosene as a longer chain version of hexane, it will be similar to nujol.
One thing you may notice is that when you mix some cooking oil with kerosene is that the water (if there is any in the cooking oil) may separate from the organic liquids. This may make it go cloudy. But I think that the organic part of cooking oil (fatty acid glycerol esters) will be miscible with kerosene.