Haha,
now that the panic has died down a little, is it too late to mention that the resistance of nitrile or nitrile blended rubber to white spirit, petrol and paraffin is classed as 'excellent'?

Probably just as well, since it's used so frequently for fuel hoses on cars...

Fwiw, I've dunked many breathers in petrol, diesel, domestic burning oil or whatever else was to hand, left them to marinade for an hour or so, then blown them clear with the air line set to as high a pressure as possible.
It certainly doesn't seem to have harmed them and in many instances seems to have got rid of the carbon deposits resulting from neglected oil changes or overheating.

ken
( btw, the air was directed through the breather in the same direction as it would normally pass.)

Thanks Ken

Its a wonder 2CViking hasn't responded to this. He would say bin it and replace with a new one. Their life expectency isn't very long - about 5 years. I replaced mine with an ECAS special one that never wears out. Works on a simple reed valve principle and gives good positive crankcase ventilation (PCV)

The problem is that once they gunk up, crankcase pressures build up. So longer term, a stuffed breather causes a stuffed engine. Then you have to replace both.

Daffy Duck

I fitted one of the ecas 'reed valve' ones to one of Dawns cars and I must say I am impressed, expensive though but it'll last longer than 5 years.

They seem expensive for what they are, but assuming you buy a new one every 5 years, spread the cost over that time and it'll be a tiny fraction of your fuel/insurance bills.

Well oil breathers now days are more or less useless. The original breathers worked very well and for a long time. Reproduction breathers performances are low and short. Do a test with a water manometer and you will see very little vacuum at high rev. It may work OK at idle but the vacuum is needed at high speed but in many cases close to 0. Even the English made has poor readings. Reproduction parts are ‘’normally’’ made from low quality material. Yes Daffy Duck and Russell hit the nail on the head. Bin them every so often, consider the oil breather like any other consumable part or buy the original breather. OK it is old stock and expensive but it works.