Maybe they have machines for that, like they do with tires.
I wish I had a machine that would just do my makeup for me. 
It would be great if you could remember your source, but hey, that’s a neat piece of trivia! I’d pay attention next time I rewatch Cars. 
I think Cars handle delicate items with a ‘utilty arm’. I got this idea from Shiftwell’s bio:
In the case of guns (both the spray paint and the bullets kind), if you read ‘The Art of Cars’, you can see that it is attached to their hubcaps through a bolt-like ring. I think it’s in one of Ramone’s concept art sketches. Of course, then it raises the question of how they slip it on in the first place.
Also, ‘The Art of’ mentioned that the designers made male cars angular and boxy, while female cars had more sleek and feminine curves.
It’s quite interesting to ponder what car models would be ‘coded’ as which gender. Sometimes when I’m on a car trip and I’m bored, I try to assign genders to cars I see passing by.
So, a Ford Mustang, Mitsubishi Lancer, and a Mini would be ‘male’ cars, from their huge and/or angular shapes. And a Holden Barina, Dodge Viper, and a Nissan Micra would be ‘girl’ cars, from their small and/or curvy shapes.
Another way to tell is what kind of target markets the car models are sold to. So Subaru R1, Toyota Picnic (my family’s car), and Mazda Miatas, which are frequently sold and appeal to women drivers, would be ‘girls’ in the Cars world. And Ford GT, Aston Martin DBS, and Humvees, which are frequently sold and appeal to men drivers, would be ‘guys’.
It’s like how you tell the robots in Wall-E apart. Does my reasoning sorta make sense?
About the make-up thing. Very true. I actually never noticed that about the Minnie part. Anyway, it’s always really easy for me to tell the gender, i dunno why, i can just feel it. LOL 
I’ve never had trouble with their gender, either. But that could be because I pay too much attention. 
Well, let’s think. A female car would have 2 exhaust bins, and a male would have one…
Actually, that only really raises further questions. For instance, since Cars have in fact realized the need to have arms- such as to handle delicates and other small objects- why is such a beneficial device only for issued for spies and not everyone else? Auto engineers, Car Doctors or even for regular use, why would such a useful tool only be allowed for a set number of individuals, how come more Cars can’t have this? Is it because of the price and if so why not just build a low grade one?
Very good point, thedriveintheater except I was thinking something exactly opposite. In the WALL-E Universe, aside from being able to tell from programming and color it’s in fact [i]very[i/] difficult to tell genders apart. Point in question, D-Fib. It’s job is that of a paramedic, which by historical constructs would indicate it’s a male, it has a dark blue stripe across it’s side the same as VAQ-M or BRL-A. And yet it’s a she. Same thing with M-O too, before I even knew how to pronounce his name I thought he was some kind of Nun or something just based on the Eric Tan promo art.
I think a better question for this thread is not “How” to tell a Car’s Gender but “Why” it even matters. Cars can’t reproduce (and please please please don’t go into a counter example using fan biology) and are animate inanimate objects so what difference does it even make? And don’t tell me it’s just because of the personality- what about homosexual cars or transvestite vehicles? Who’s to say a lesbian car is really a female car at all? I don’t think PIXAR really thought this through enough.
But it is clear that a child or whatever you want to call it can be created. And I am NOT saying this based on a fanfic. Although I have read one… 
Anyways…there is a child in the stands in the first movie. As for lesbian cars etc. I don’t really have a comment, I don’t understand what you’re saying? 
Other cars are able to use them. Luigi is cleaning his windows with an arm, Ramone paints with a paintgun arm on his hubcap, etc. The arms don’t necessarily have to be long.
Actually, they can have kids. You see one in the movie itself. 
Kind of makes you think really weird things. You need to remember that they’re inanimate objects to us, but we’re not talking about our world anymore; we’re talking about their’s.
Does it matter how they have kids? No, because some things are just left unexplained. 
No, but on a serious note, it’s a movie. It’s fictional, so even if we were able to understand these things, it still wouldn’t matter.
In my fanfiction, I don’t explain how Lightning and Sally have their baby or how it comes to happen - simply because I think that things that weren’t explained shouldn’t be explained and…well…other fanfictions creep me out. 
But, let’s say this world does actually exist - for the sake of conversation. As for homosexuality or bisexuality, I think that exists in their world. I mean, if a male and female car can fall in love in their universe, why should it be a problem the other ways around? It was already made clear that they have genders; they have different bathrooms, different voices, the girls wear makeup, etc. They’re also able to have surgery. I know this because in Mater-National, one of the monster trucks taunts you in your race saying something like, “When I’m done with you, they’ll need to prepare you for surgery!”
It has been proven that homosexuality exists in other animals on our Earth, so if the Cars universe is a parallel of our universe, I wouldn’t think that it doesn’t exist.
Honestly, I don’t really care, but I think these conversations are really fun because it makes you think a lot. 
I wonder how Chevron pulled it off…
You are totally right jessie! It is obvious that Cars do have genders and can have children. Great points! 100% agree 
Aww thanks!
No problem! I love your posts, I’m gonna add you as a friend
Thank you! Always nice to see another person who loves Cars here.
Oh yeah. It can be hard to find them sometimes if you know what I’m saying!
Well, at least we have a couple here. They are really hard to find in general. Anyway, I always thought their genders were pretty easy to pick out.
Yeah for sure 
Me too, never really had a problem with it. I think this topic has basically been covered. I dunno what else to say! 
Ok, let’s get back to the point. I’m seeing a lot of contradictions and flaws with the explanation to the anatomy between female and male cars, and i’ve been going a little too subtle to be entirely convincing, so i’m going to lecture you a bit:
Let’s say, for example, that cars function in gender’s between different car companies, use of oil, and how they represent theirselves emotionally and metaphysically. Porsche is one example, Porsche is a luxury vehicle and sometimes, could be displayed as a feminine type of vehicle (let’s just throw it down, I don’t want to admit anything). It’s more feminine, but not entirely. Let’s say that Pennzoil is Female, and hard-boiled Gasoline is Masculine. If they ran on Pennzoil, you get Female, Gas, Male. And Kerosene, well, that’s for any car that’s in between the other two. Now, if the ‘female’ car acts with complex emotions, likes to get into detail with situations, yes, that’s a female, but, if the car has simple emotions, and casually gets to the gist of the situation with barely any debate, practically, someone says ‘let’s do this’, and everybody does it, no arguments, that’s the male car. So, three different characteristics, less obvious characteristics, suggests the sex of a car: Car Company, Oil Use, and Emotional Aspects. Since this is an odd number, there is no debate over which car is female or male, since one will top out the other 2/3. So, let’s say Sally has 3/3 of the female characteristics (Pennzoil, Porsche, Female Personality), yes, that’s how you can tell a female. And, let’s say Lightning has 2/3 of the Male, he still is a male, with some female personalities or aspects as well. If you can’t get to the physical details of a female or male, then you might as well go the subconscious and emotional aspects.
Note, these are only examples, but they convey a mad lib’s of how gender’s could be interpretated between vehicles.
Obviously, because there’s no such thing, but in their world there is. We don’t know about them though, so there’s no possible way to explain it - though we get the general idea. Sally sounds and looks like a girl. Lightning sounds and looks like a guy.
As for that whole oil thing you went off on, I honestly didn’t understand any of that. 
I was just throwing off something, i remember watching an episode of Futurama were female robots and male robots had different types of oil in their system, the female’s was femmzoil, but i don’t know the men’s. That’s practically where i got the idea.