Totally don't use, creosote or motor oil... town I went to school near us is actually a 'super fund site' from a railroad tie factory and creosote, pretty sure it must have been coal creosote , bad, wood creosote not much better, but almost similar to , but not, to smoking meat or using liquid smoke, that we eat..., It's a preservative, either way.
Locust fence posts need no preservative, last forever, ... but if you used other than, dad always soaked them in a bucket of creosote, I'm pretty sure stuff he saved himself from what leaked out of the wood stove.
Not even joking about guy I work with said he painted his barn with motor oil, many yrs ago and still looks nice,... no thanks. .
Some people here actually ran barrels of used motor oil, sprinkling it up and down their roads to cut down on the dust, dirt roads. Most roads are now tar and stone and not dirt blowing up a dust cloud (more motor oil) eventually wore down and much like actual blacktop (more motor oil). Roof shingles, more motor oil, ...
Blah blah blah blah....