I have an oil fired central heating system in my house and whenever it fires up the boiler has started to make a very loud whining noise, the heating and hot water still work ok but every now and then there is a strong smell of fuel from the boiler
It sounds like the pump or the fan is starting to wear out and could pack up anytime in the not so distant future. Probably according to murphie's law on the coldest day of the year no doubt when you need it the most !!!
Probably best to get it checked out before winter hits mate.