What is the ratio for bar oil verses gas? Should they both run out about the same time? I have a Husky 137 that seems to only go through 1/4 to 1/3 tank of bar oil for 1 tank of gas. It seems like it needs more oil, the chain dulls pretty quick and usually have to run a file after every tank of gas. I've checked and cleaned the oil port....no clogs that I can see.