When a saw runs out of fuel, it is typically running lean. Some of my saws just bog down and quit, others start to rev up. That said, despite what horror this causes for some, I don't think it harms the saw in any way. It takes more than a few seconds of running lean to harm the engine. What causes a piston to meltdown on a saw that's too lean is heat. Not lack of oil due to lack of fuel. It takes a while for a piston/cylinder to get hot enough to create transfer. How long? I don't know but I do know it's a lot longer than the several seconds a saw will run when the tank is empty. Every time a saw gets tuned, it's running lean briefly. Briefly is the key word here.