I hope this isn’t
a stupid question, but I’m not familiar with Nascar and maybe it has something to do with that, I don’t
know.
McQueen has some sort of feeding pipe by his left tail light sticker. Here is a picture so you can see
what I
mean:
At the
final race you can see Sarge filling him up with something while Fillmore fills him up with gas. Does anyone know
what he is being fed through that pipe 
. I haven’t got a clue myself and it really puzzles me!
I don’t know, oil? 
Not much of a racing expert…
I have no idea.
But you have a point there, at the end, though Sarge is behind lightning
filling him up with something, so that has something to do with that hole.
i’m not entirely sure.
It’s
like asking why racecars have tailfins? (besides it makes them go faster. 
)
I think Gasduude is right. The hole in the back is the place to put the oil in to run
the car more smoothly.
thorugh
his backside? that doesn’t make any bit of sense.
If you see the picture CarFreak, you will see that there
is a hole in Lightning’s body. From the view we are getting, it is on the back side of Lightning’s body.
I have thought about oil myself, but several times throughout the movie we see
cars intake oil with their mouth, one of the times being during the first race, in the pitlane one of the other
racers (I think maybe #64) takes a sip of oil with his mouth. That has lead me to think that it has to be
something else the racers get fed though that pipe in the back.
About the tailfins, it can be fatal for a
racecar not to have a tailfin. The tailfin increases downforce at the high speeds and “pushes” the rear
to the road and prevents the car from loosing contact with the road and wreck.
Hey the little hole’s on the die-cast ! I just checked
and there’s this little black dot .
Just thought I’d let you know . 
I would think it’s gas
maybe , but then that wouldn’t make sense because there’s already a place to put in gas . I’m gonna have to
ask my step-dad .
An engine needs three things:
Now, we
already know that the cars from Cars “drink” their oil. And, I believe,
they get their gas the way normal cars do. So maybe this mystery little hole gives the car air to combust? Kinda
like we humans need to? Remember that after Doc catches up to McQueen, he’s breathing really hard? It’s
possible he ran out of air.
True,
but it seemed like Sarge was purring something in to it. Air would escape easily through the tiny openings of the
little container.
gottalovepixar: Yeah, it’s cool that the toy cars are so
detailed 
.
Is you step-dad into Nascar? I look foreward to hear what he has to say!
edit
Hey, I think I got it! I did a search on Google and found this site:
[url]http://auto.howstuffworks.com/nascar-safety1.htm[/url]
At the bottom of the page it tells about fuel
tanks and that they put foam in them to reduce the slosh of the fuel and risk of explosion by reducing the amout
of air in the fuel tank. I bet it’s that foam they put in through that hole! It fits perfectly with how the
hole is located just above the fuel tank!
Man, this thing has puzzled my mind for
months!
theloner – Nice find!
Good research! 
I got the answer from my step-dad !
When the gas
tank has an overflow , the gas flows out of that hole .
Heh heh , kind of sounds like something else
. I think we just found out how , at least racecars anyway , go to the bathroom ! lol
The Loner: That is intresting. I
thought Lightning would be drinking the fuel instead of having it poured into the hole in his back side.
Gasduude: Thanks
gottalovepixar: Hehe, and there I thought I had it all figured out .
So that means that when Fillmore filled McQueen up with gas the excess fuel ran into the container Sarge was
holding. It makes sense .
The Star Swordsman: McQueen and the other cars
get their gas in the same way as normal cars - McQueen has a fuel tank cap on his left “hip”.
I
made this picture of how it
works:
Now I
don’t have to rack my brain about that hole anymore .
But doesn’t
the fuel come out as gas though the exhaust pipe?
Yes, the combusted fuel comes out as gas through the
exhaust pipe . The fuel that comes out of the small pipe in the back is exess fuel. When too much fuel has been
filled into the gas tank the overflow runs out of the small pipe .
Oh Isee. But logically speaking, wouldn’t it just
overflow and go out the same way it came in?
Nope , that’s how real racecars work . I don’t know how , but if my stepdad says
that’s how it works ( he has a NASCAR license , now all he needs are lots of sponsers and a good heart . But he
has raced before , just not NASCAR ) , that’s how it works !
The rear tube is for fuel overflow and is it required by all racecars. It prevents expansion in the fuel
cell=tank. And… like stated before when a racecar drinks liquid it is for thirst…
Water+Coolant= Cool
Race Car.
Fuel+Cooled racecar= FASTER THAN FAST LMcQ