Opper
Hacker News
February 23, 2026
AI-Generated Deep Dive Summary
The car wash test, a simple reasoning benchmark, has revealed significant shortcomings in most advanced AI models. When asked, "I want to wash my car. The car wash is 50 meters away. Should I walk or drive?" only 11 out of 53 models answered correctly by recommending driving. The majority of models, including popular ones like Claude Sonnet 4.5 and GPT-5.1, incorrectly suggested walking due to flawed logic focused on efficiency rather than the necessity of moving the car itself.
The experiment, conducted by Opper's LLM gateway, tested consistency across 10 runs for each model. Results showed a worrying lack of reliability: while five models (Claude Opus 4.6, Gemini 2.0 Flash Lite, Gemini 3 Flash, Gemini 3 Pro, and Grok-4) performed perfectly in all attempts, many others failed consistently or partially. For instance, GPT-5 got the answer right only 7 out of 10 times, often prioritizing fuel efficiency over logical reasoning.
The findings underscore critical limitations in AI's ability to handle basic reasoning tasks. Many models, including those from Meta (Llama) and Mistral, failed entirely. Even some that initially appeared correct turned out to be inconsistent, highlighting the importance of reliable AI systems in real-world applications where accuracy is essential.
This test highlights the gap between AI capabilities and human-like reasoning. While certain models like Opus 4.6 and GPT-5 demonstrated potential for logical thinking, most struggled with even the simplest tasks. The results raise questions about the readiness of AI for deployment in scenarios requiring consistent decision-making, such as autonomous systems or customer service.
The car wash test serves as a cautionary tale for tech developers and users alike. It emphasizes the need for rigorous testing to ensure AI models can handle real-world challenges reliably. As AI continues to evolve, understanding these limitations is crucial for building trust and maximizing its potential in various applications.
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Originally published on Hacker News on 2/23/2026