Can used engine oil be used to lubricate bar and chain?

The use of waste engine oil is not recommended for many reasons. Some of those reasons are: 

1. Waste engine oils frequently contain small particles that will damage the oil pump over time resulting in expensive repairs.
2. Waste engine oils cause deterioration of rubber components over time, again resulting in expensive repairs.
3. Waste engine oils do not have the tackifiers to keep the oil on the chain where it is needed to properly lubricate.
4. Waste engine oils may contain acids and or carcinogens from combustion by-products.
5. Waste engine oils frequently contain heavy metals which are both harmful to the environment as well as humans and animals alike.

When disposing of used oil make sure to do it accordingly since used engine oil can be detrimental to the environment.