There's been a lot of discussion elsewhere about the real value of a standard Nomex flight suit in terms of fire protection. But anyway I wear mine when flying the heli not so much for fire protection but because the preflight (R44) involves grovelling around on the ground, which I prefer not to do in my best clothes. I bought it for flying the Pitts, again not so much for fire protection (with the fuel tank right above your knees, in the front seat at least, I'm not sure really how much good it would do) but because of all the handy zip-up acro-proof pockets.
I'd feel a bit silly wearing it to go for a day out in the 182, although the pros (Police etc) wear the full gear including helmet even in a 182.
n5296s