Hi wood spinner, you can also adjust the amount of oil that comes out on to the bar by adjusting the oil pump its a 1 - 2 -3 setting for different sized bars.
no 2 is the normal setting for an 18" bar, when running your chainsaw the petrol should run out before the oil so not to let the chain run dry and cause damage to the chain and bar. I hope that this helps . les
13-15 no 1
15-18 no 2
18-20 no 3