On Wed, 2 Feb 2011 08:07:16 +0000, Piers Finlayson wrote:

My oil fired boiler has started whistling while running. The
high-pitched whistle starts about 10s after fireing up,

Define "fireing up" do you mean blower starting or when the ignitor
fires to light the boiler some seconds later?

Thinking that it might a worn jet if it hasn't been serviced/replaced
every year or so. Though I'd expect that to stop PDQ after the blower
stops.

Kettling due to scale can be quite high frequency but I wouldn't call
that sound a "whistle", ie a single tone, it's more high freqency
noise.

--
Cheers
Dave.