Preheating a car at +5C is just ridiculous if you are using the
proper
weight of motor oil. I might use a block heater if the temperatures
went below -20C, but not higher than that. Try using a good 10W30 oil
between +5 and -10, and perhaps a 5W30 below that. You won't damage
anything, and your engine will last longer than the body panels on the
car!

I use 5W30 year-round in my '01 Chevy. Runs just fine, and
it's what the manufacturer recommends for our climate. The tolerances
in these auto engines are now so small that anything heavier is not
only a waste of time but could be really bad in the cold.
Aircraft engines have much larger tolerances, mostly because
they're air-cooled and get a lot hotter, with clearances between
things like aluminum pistons and steel cylinders getting pretty tight
at high temps. Aluminum expands at twice the rate of steel, and while
some pistons have steel inserts cast into them to control that
expansion, they still expand a lot. Liquid-cooled engines can be built
much tighter. And auto engines have much smaller cylinders than
aircraft engines of the same HP and so the overall expansion is less.
Rings are either chomed steel or cast iron and will expand at around
the same rate as the cylinder, but they'll still get tighter from the
heat draining off the piston through them. They have a bit of
difficulty getting rid of that heat through the microscopic oil film
on the cylinder wall.
With larger tolerances, more oil escapes. With larger
tolerances, the arc of contact area is shorter. With larger
tolerances, things tend to strike each other harder. So heavier oils
are necessary to slow the oil's escape from bearings and so on,
heavier to lubricate the shorter contact arcs, heavier to dampen the
shocks of parts banging into other parts.
Piston scuffing often happens when an engine is driven to full
power too soon. Pistons get hot and cylinders are still cool,
clearances disappear. Scuffing can happen if the oil isn't reaching
the cylinders, and since it's usually thrown off the rods (some
engines have a squirt hole in the rod opposite), a really low idle
might leave the cylinders dry. Some two-strokes like the aircooled
Rotaxes must be warmed up thoroughly or they'll seize soon after
takeoff. Local guy learned that the hard way. Seized it twice before
someone clued him in.

Best things for folks who fly infrequently include installing
a preoiler and don't make short flights. The preoiler will fill all
the oil galleries and pressure will come up even before start. The
short flights leave water in the oil the eat the engine. The folks who
"run it up once in a while to keep it healthy" without flying it are
doing the worst damage by far.

Dan