Can you use 2 cycle engine oil in a lawn mower?

Depends on the lawnmower. Some older lawn mowers used two-stroke engines, and you mixed the two-cycle oil with the gas. But 99% of modern lawnmowers use a four-stroke engine with a crankcase. So if the question is: "Can I use two-cycle oil in the crankcase?" the answer is an emphatic NO. It will likely destroy the engine.