RAW has nothing that can be enough for your players.
I could not find anything that would easily duplicate gasoline, although there is one thing I could find that your players could use, an Alchemy Jug.
This article can produce a defined amount of a list of liquids once a day. Among this list is "oil". Given the inaccuracy of this phenomenon, your players could eventually produce this oil and refine it in gasoline, but there is a problem, there is only a quarter of a liter a day. At most, you get 3 / 4th of the amount of gasoline you have in the oil, so you can get up to 1.5 liters of gas for 1 liter of oil. 39; oil.
The big problem with this is that no reasonably level spell would allow you to magically refine the oil; you should therefore use conventional equipment to do it, even if you could use magic to produce the energy input for that material.
As far as spells are concerned, your players would have two options.
First of all, they could use Wish, but as creating a mass of liquid is not part of the standard options, there is a one in three chance of losing Wish, plus the danger inherent in unforeseen effects, which means that better choices are present if you use this spell.
Secondly, they could give up gasoline and use Animate Objects, but that requires a level 5 niche, a concentration, and only works for one minute at a time.
Your players have a chance however, YOU. You may decide that an alchemy jug can produce gasoline itself, or allow a product to reflect to produce it (such as the carafe of endless water). Assuming you want them to use the car a lot.