On this claim, Snopes says
While a mixture of raw egg and water
vigorously stirred together in a glass
will produce a somewhat milky-looking
liquid (which might be the source of
this tale), there's nothing about the
interaction of egg and water that
renders the resulting combination into
a substance guaranteed to completely
block a driver's vision. Egg alone or
egg-and-water solutions are thin
liquids and so are relatively easy to
see through, with the vehicle's wipers
generally sweeping away the worst of
the mess fairly easily. Moreover, it
would take a number of extremely
well-placed eggs (a hen's typical
offerings aren't that big) to splat a
windshield so thoroughly as to
completely impair the driver's view
and force him to stop immediately -
unless the visibility conditions were
already poor, a motorist with a
splattered windshield would generally
still to be able to see well enough to
continue driving out of range of the
egg-throwing hooligans to a safe
The 92.5% claim seems totally bogus. Is it 92.5% of the entire windshield or 92.5% of the driver's direct visible area - assuming the driver is looking straight ahead on the road. Let us assume that any spreadable surface area under the wipers - on any model of car - will be affecting the driver's direct visibility since that's what wipers are meant to keep clear in the first place.
Even if there is a light milky substance on the windscreen, how badly does that obstruct vision?
This gent actually tested this in 2007 with a single egg and on two different cars. You can see the outcome with pictures.
Even armed with decent wipers, it can get blurry at night but does not seem to be enough to obstruct your vision.
He concludes it's not safe to turn on the wipers but based on the images, I think this needs more testing with a larger number of eggs to be convinced.