2
Can’t Stop
Thinking About
// STRANGELY COMPELLING AND COMPELLINGLY STRANGE TOPICS OUR STAFF IS OBSESSING OVER //My Dirty Car Has
a Dirty Secret:
It’s a Surprising
Gas Guzzler
For a brief moment, the
world came close to having
an always-clean car. In 2014,
Nissan covered what it
called the world’s first self-
cleaning car in Ultra-Ever
Dry, a nano-paint technology
that repels particles like
mud, rain, and oil. The auto-
maker applied the treatment
to its ’14 Leaf model in North
America, but a spokespersonconfirms it wasn't used on
other vehicles.
While Nissan didn’t
reveal why its experiment
stalled out, experts say the
tech isn’t quite there yet.
“My experience with some
coatings has shown they
aren’t robust enough to
handle long-term weath-
ering, they can be scraped
or wiped off over time, andthey need to be reapplied,”
says Julie Crockett, an
associate professor of
mechanical engineering at
Brigham Young University.
But hope isn’t dead, she
says. “As research improves,
allowing for more robust
surfaces in more applica-
tions, I believe we’ll start
to see superhydrophobic
surfaces in our daily lives.”COULD
A CAR
CLEAN
ITSELF?
CAROLINE
DELBERT IS A
WRITER, AVID
READER, AND
CONTRIBUTING
EDITOR AT
POPMECH. SHE’S
AN ENTHUSIAST
OF JUST ABOUT
EVERYTHING.
HER FAVORITE
TOPICS INCLUDE
NUCLEAR
ENERGY,
COSMOLOGY,
THE MATH OF
EVERYDAY
THINGS, AND
THE PHILOSOPHY
OF IT ALL.
▶My car’s exterior seems to always be dusted
with dirt and other gross gunk, which makes
me wishfully wonder: Could there be an aerody-
namic upside to all that debris?
Years ago, the MythBusters team examined
whether a dirty car got better gas mileage as the
result of a possible golf ball–like “dimpling” effect.
Using the same vehicle for consistent results, their
dirty car got 24 mpg, while the clean version made
it to 26.4 mpg.
Let’s say the average person drives 10,
miles per year. Using the MythBusters results,
the driver of the dirty car will use 417 gallons of
gas per year, while the driver of the clean car will
use 379. That’s a not-insignificant difference
of 38 gallons per year. The national average gas
price is $4.10 as of press time, according to the
U.S. Energy Information Administration, which
means the driver of the clean car saves $155.
per year.
If an average gas-station automatic car wash
costs $7, the driver of the clean car can wash theirvehicle as frequently as once every four weeks
and still come out ahead. In reality, drivers are
likely to remove big pieces of dirt themselves for
no additional charge using the gas station’s com-
plimentary squeegee.
Now, what about matte car finishes? A true
matte finish is essentially just a controlled,
attractive coating of some chemical “dirt.” In
2016, the Red Bull F1 team introduced a matte
finish that keen-eyed observers pointed out is
actually a gloss finish with a special layer of
microparticles that trap the light. But in 2019,
the Ferrari F1 team switched to a true matte
finish, citing an overall lighter weight that
could save critical milliliters of fuel. So if you
wanted a sleek matte finish, you’d need to fully
remove your car’s existing finish and start from
scratch to make that switch aerodynamically
worthwhile.
This argument also explains the 10 percent
mpg difference between MythBusters’ clean and
dirty cars. Adding dirt to the outside of the car
also adds weight, and in their experiment, they
covered the car until it looked like the Jeep at the
end of Jurassic Park.
I’m a wonk for cost-saving life hacks, so if
you’re keen to improve your gas mileage like
me, these are the tricks I use: Accelerate slower,
drive slower, and follow the car in front of you less
closely so you’ll require fewer taps on the brakes.
But for a real F1-style microsavings, fill your gas
tank to three quarters every time to save about
6 pounds per gallon on your overall weight.
Mmm...sweet fuel economy.10 May/June 2022
COURTESYNISSAN(CAR);^ COURTESY^ CAROLINEDELBERT^ (HEADSHOT)