I had a 3818 that quit oiling.
I dumped the bar oil out of the tank and filled the oil tank with kerosene.
When I ran the chainsaw the kerosene went right on through the system and out on the bar and chain.
After that I ran 10W-30 - 10W-40 motor oil for bar oil.
I also had a 3214 which seemed to always oil OK but the 3818 always had trouble putting enough oil on the longer bar.
The 3818 had a replacement Oregon bar on it with the tiny angled oil hole. I drilled this oil hole out to 5/32" and the oil situation was much better.