I use silicone grease on my pump, there's no metal to metal contact, it's all metal to O ring sliding surfaces.


'The debate about mineral oils (fuel), high pressure/temperature, oxygen/air ratios would seem to be deserving of a thread on its own?'

Instead of starting a new thread on the subject, just Google 'high pressure air mineral oil explosion risk':

https://www.google.co.uk/webhp?ei=f2...explosion+risk

It's not really something that needs discussion, it is what it is.