I coppaslip the wheel-to-hub bits, and the taper of the wheelbolts. Its the only way you stand half a chance of undoing them with the shite wrench that GM supply at the side of the road 
I rejoice that Omegas carry full size spare wheels and the tools to change wheels at the roadside. So many cars these days come with space saver skinny wheels, or, worse, no spare at all, just an aerosol of porridge to squirt into the flat tyre in the vain hope that it will plug the hole and reinflate it - that's no good to me.
I carry an extensible wheel nut tool and a torch too, and a tool roll. I do not yet carry a spare crank position sensor, but I think I should.
FL spare wheels count as (almost) a space saver, hence the 80kph stickers all over them.
I don't recall any such sticker. I keep buying used Omegas on e-bay, all come with unused spare wheels, steel wheels fitted with assorted makes of tyre, all 205/65R15 94H tyres. My 2.5 estate is currently running on four of them, and the spare is a brand new similar wheel. It seemed a shame to waste them.
I have heard say that one should not use 10 year old tyres, but I cannot see why. The tyres on my Stoic lawn mower are 50 years old, and look good for another fifty years. I think it is daylight that causes them to crack.
Now you mention it, there may have been labels on them, now hidden under hub caps. Yellow curved things, with printing on them. Perhaps they feared that mixing tyres of different sizes would be unwise.