More car sales using an "AI Brain" ?

Tldr: I built an "AI Brain" (technical term is a RAG) for a car dealership and I made sure to test multiple approaches to make sure it's as accurate as possible, while optimizing speed of response and minimizing the cost.

Hey guys, my background is AI research and development, both in industry and academia, and I wanted to build an "AI brain" for a car dealership.

Meaning a system that could answer questions like "On average, how much do your BMWs cost compared to your Mercedes cars?". This system would use all the cars listed from the dealership website as well as the reasoning of LLMs like chatGPT to answer as accurately as possible (meaning no hallucinations), as fast as possible, with the minimum cost possible.

I did not want to build this just for the sake of building it but to integrate it inside a sales system like a speed to lead system.

The awesome thing about building an "AI brain" for a business is that after it's built, it can be integrated in many things (instagram page, landing page, voice bot etc...)

For example if a car dealership run ads and calls leads as soon as they opt-in with an AI voice bot equipped with this "AI brain", that would definitely lead to an increase in car sales. And using realistic numbers I found it would bring an extra $10,000 / month for a small car dealership that has around 150 cars listed.

Anyway I decided to run the numbers and I also documented everything about how to build this system where I compared multiple approaches using the same metrics, to check which one is the best.

It turns out using gpt-oss-120b is the best one for accuracy, cost efficiency, and speed (for this specific use case). On average, this model generated an accurate answer in 2.8 s, with a cost of $0.001 per question.

It provided even better results than both Gemini 3 and gpt 5.1 !

So if you're a business owner and you're thinking about building something like this for your small business, you shouldn't believe the hype videos on youtube (like "Gemini 3 just crushed everything") and make sure the AI professionals you hire are comparing all possible models with objective metrics to make sure they'll choose the best ones for your specific use case.