As we know that any direct material which has insignificant value is considered indirect. So other way round, if any indirect material with a significant value is considered direct?
But none of the lubricating oil ends up in the product so it will be indirect.
The idea of treating material of insignificant value as indirect is simply an accounting convenience. If you were making furniture and as a final stage applying polish I don’t think it’s worth the effort working out how many milligrams are applied to each piece of production.