Chain lube usage rate

[JamesTX]

Is there any rule of thumb concerning the rate of usage of chain lube - i.e. a tank of lube per tank of gas? Or is there enough variance in saws that this isn't a valid question?

I have a Stihl MS 250 if that matters.

 

[ray benson]

Almost a tank of bar oil to a tank of gas.You don't want to run out of the bar oil and still be cutting.