Many, many moons ago I stopped for a couple of days helping out with some mustering in the Hughenden area of Queensland (OZ). Hughenden is inland, very hot, very dry and has an airport a couple of miles outside of town with a sealed runway. I was flying a Hiller12E which had a stainless steel muffler fitted to the Lyc VO540.
Before I headed off for the 2,500 mile trip to Port Hedland in Western Australia to do some Uranium exploration, our company sent up an engineer and apprentice to do a scheduled 300 Hourly inspection on my machine. We were just buttoning up the machine when a military 0H58 landed outside the terminal looking for the refueller to come out from town to supply Jet A1.
When I saw the four sprogs (they must have been on a NAV) standing outside their machine in 50 oC heat coming off the tarmac, I figured that anyone who didn't know to go sit in the shade in that climate was some one we could have a bit of fun with.
So.... the engineer and I poured near enough to 10 litres of the old engine oil (W100) into the Hiller's big muffler and then emptied the Aeroshell 14 in the grease gun into the muffler as well to make a thick hydrocarbon soup. We double checked all was OK with the Hiller and then sent the apprentice over to say hullo to the sprogs.
The conversation went something like this: "Gidday mate what's happening with the Hiller?"
" Oh - nothing much. Tc said it was burning a bit of oil so we had a dekko at it and fixed it up before he heads off to WA."
Seeing the apprentice then giving me the secret sign - I cranked up the Hiller, engaged the clutch and warmed it up at the lowest revs I could. The engineer gave me the all clear that there were no oil leaks and I then gunned off the Hiller into the setting sun at Max allowable power and at about 100 Ft AGL. You can imagine the smoke screen pouring out the muffler pipe - they said it looked like a WWII destroyer trying to hide a whole battle group of ships.
The sprogs' jaws dropped at the sight and then they just about had a heart attack when the apprentice calmly said: "Yep - it looks like its going a whole lot better now!!!"
True story