First I need to know if you actually drive a Maserati, because if you do I don't think you will have a problem
There are several ways to convince a girl to have car sex but I'm gonna focus on the easiest one, first off, find several good spots around your/her area.
Here in San Francisco there are several really famous spots where people commonly park to fuck, Twin peaks for example or many of the Vista points around the mountains in Berkeley where you also have a beautiful view!
Ironically, most of the times that I have decided to have car sex (even tho I have my own condo) it is parked on some corner off a busy road, mostly because we were both too horny to drive home first!
Ok so find an excuse to park at your spot, making out is a great excuse.
So start making out, kino escalate do all of your regular shit you would do in the bedroom, and then as the intensity increase you can hear her moan, you rub your crotch or your hand against her crotch, this is when you unzip your pants and take your dick out. Sounds crazy? Well it isn't cause she is a girl, she is horny or else she wouldn't make out with you and she knows what to do when she sees a cock. All girls do, she will start playing with it and after that it is up to you where it leads, but the times that I have done this it ends up in at least a hand job and often more than that!
Just remember to keep febreeze and wet wipes in your car
The other issue that you need to consider is the size of your car, in a regular 4 door it is usually never a problem to have sex in the back seat in multiple position, but if you drive a coupe (or worse, a 2 seater) it may sometimes only work if she wears a skirt, cause remember, many girls prefer to not get completely undressed during car sex, part of the thrill is to keep a lot of clothes on and just kinda "slink it in".
But have fun with it, experiment, and don't be afraid to "flash your weapon"

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Slywalker
10 things I wish someone taught me about Pick Up
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