Every unit is its own stock item
Ordinary inventory counts quantities of identical things. A showroom does not: each vehicle has a VIN, a specification, a cost, an age on the floor and often its own financing. Odoo handles this with serial-number tracking, so a unit is traceable from arrival through test drive, reservation and delivery, and its individual holding cost is visible rather than averaged into a pile.
The workshop and the showroom share parts and rarely share a system
Service is where the margin quietly lives, and it runs on the same parts inventory the showroom draws from for pre-delivery work. Keeping repair orders, parts issue and job costing in the same database is what stops the two sides reconciling by spreadsheet at month end.
Trade-ins are a purchase disguised as a discount
A trade-in taken against a sale is an acquisition at a valuation, not a price reduction. Recording it as its own inbound unit keeps both the real selling margin and the true cost of the used unit intact, which is the difference between a used-vehicle desk that knows its position and one that does not.
