the eff. firing gas has three varibles going for it which COULD make it more eff. These are:
1. Less excess air required, therefor less heat loss due to excess air.
2.Lower flue gas temperatures can be obtained as you do not have to worry about acid dew point in the stack gas.
3.Better heat...
The first thing to do is make sure the pump is not "sucking" air on any of the suction piping or its casing.
What oil does the manufacture recommend ?
Have the oil analysised, contact your oil supplier, they often will do this for you. The oil compinies have engineering staff that...