The Massachusetts Executive Office of Public Safety and Security offers this checklist for oil burner maintenance:
Oil burners and boilers should get a cleaning on an annual basis. Someone should always be present with the service technician while in your home. When paying for a boiler / burner cleaning, make sure that the following is done:
e_SBlt The oil filter is replaced
e_SBlt The burner nozzle is replaced. You may also want to ask the technician to show you the gallons per hour and the type of nozzle. Make sure that it is the similar to the one removed.
e_SBlt The oil pump strainer is replaced
e_SBlt The chimney and flues are opened and vacuumed clean
e_SBlt The boiler is opened up and brushed/vacuumed
e_SBlt The oil line is purged of air after the parts above are replaced
e_SBlt The chimney cleanout port is closed after cleaning and the flue parts are screwed back together
e_SBlt A combustion efficiency test is performed
Before the technician leaves, you should run the thermostat up and make sure you get heat. This will ensure the technician didn’t inadvertently shut off a pump or close a valve.
You should also ask for documentation dated and signed by the technician with the results of the combustion efficiency and date performed.