I've been doing quite a bit of research into budget cars recently, and as a result have filled in a few (Honda Civic, Nissan Versa) to something I'd consider pinned level. It'd be easier on myself, and anybody else that wants to start filling out cars if we come up with some standards on what should go into the description.
Here's my suggestion on what should be included, and each "section" which can be a paragraph, or a few sentences inside of a paragraph, that's more of a matter of style. The key is that the core information is there.
Drive train - how many gears? is it available in standard and automatic? CVT? what's the horse power? Front wheel, rear wheel, 4-wheel drive? A mention of fuel consumption is also good.
Interior space - how big is the interior? how many seats? storage capacity, with folded and non-folded seats. how much leg room?
Standard features - what comes available in ALL versions of the car, air-conditioning, radio, power windows/locks, any other amenities?
Standard safety features - disc brakes or drum brakes? how many air bags? anti-lock brakes?
Difference in trims - most car manufacturers have different "trim" levels that upgrade various parts of the car such as including spoilers, or upgrading the stereo, etc. Mentioning the key upgrades is useful.
Safety ratings - should include ratings from both the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS) websites.