Cool oneshot, but I don't really know how this could become a series. I could maybe see a second chapter with her learning manual driving and going back to that car, but the premise of "university girls in convertibles" doesn't leave a lot of wiggle room for the author. Would they just keep buying/renting new convertibles to show off the different models? Would they go into automotive engineering at university or intern at a dealership or something? I could potentially get behind something like that, but I don't know if I could get behind it with the characters as they are.
The main girl is fine, and I liked her attitude, but the car-enthusiast was such a dick this chapter, skipping class to show the mc a car, barging in and talking over the salesmen, trying to sell the unknowledgeable MC a car just because she wanted to drive it, and then changing her mind and dragging the other girl away when she had a chance to drive said car just because it wouldn't be a manual model. She created a massive problem with the other girl not being able to drive manual because 'she' wouldn't be able to drive it? While they were at a dealership? With the opportunity to test drive it? She doesn't even know if the MC will like it, and she's trying to get her to pour thousands of dollars into a car just so she can drive it, while dictating to the MC that it'll be a manual because she prefers a manual despite the MC only having an automatic license. Unless she's a gateway character that introduces the MC to a car club or something (though I doubt she'd have any friends or acquaintances with that personality) and then gets phased out, she is far too unlikable and self-centered to make for an interesting main character as she is.