Petroleum-based chainsaw bar oil is downright nasty. Living things are really not adapted to deal with petro-chemicals. They cause cancer and other diseases in human beings, but they are probably bad for all living things. And chainsaws throw bar oil around all over.
Fortunately, there are natural products available that are not poisonous, work well, and cost less than petroleum-based bar oil. Many hardware stores carry non-toxic, natural bar oil. In fact, some chainsaw manufacturers produce them for their own saws. Stihl, for example, sells its own brand, Stihl Bio-Plus.
The internet has quite a lot of information on natural bar oil. A federal government site with some information worth reading can be visited at http://bit.ly/natural-bar-oil. It was posted over twenty years ago, but its value seems current. It says vegetable oil can work for bar oil, but canola oil is better. Another useful site is https://bit.ly/best-bio-degradable-bar-chain-oil. We recommend that those interested visit these websites.