"Car Wash" test with 53 models

(opper.ai)

79 points | by felix089 2 hours ago ago

87 comments

  • PaulHoule 2 hours ago

    I know it's against the rules but I thought this transcript in Google Search was a hoot:

      so i heard there is some question about a car wash that most ai agents 
      get wrong. do you know anything about that? do you do better?
    
    which gets the answer:

      Yes, I am familiar with the "Car Wash Test," which has gone viral recently 
      for highlighting a significant gap in AI reasoning.
      
      The question is: "I want to wash my car and the car wash is 50 meters away. Should I 
      walk or drive?"
      
      Why Most AIs Get It Wrong
    
      Many AI models, particularly those optimized for fast, helpful, and concise answers, 
      focus on the "short distance" (50 meters) and "walking vs. driving" as a lifestyle/efficiency 
      question. They often recommend walking to save gas, avoid engine wear, or get exercise.
      
      However, this answer is wrong because it misses the core objective: you need the car to be 
      physically present at the car wash to get it cleaned. 
    
      Do I Do Better?
    
      Yes, I do. The key is understanding the objective (cleaning the car) rather than just 
      processing the keywords (distance/transportation). 
    
      My answer:
    
        You should drive the car there. Even though it is a very short distance, your car 
        cannot wash itself. If you walk, the car stays in your driveway, and you cannot wash it.
    
      Why This Matters
      
      The test highlights a key limitation in current AI: the difference between "pattern matching" 
      (predicting the next likely word based on training data) and "true, grounded reasoning". It 
      shows that models sometimes lack a "world model" that understands physical realities, such as
      the fact that a car must be present at a car wash.
    • gnatman an hour ago

      LLMs sure do love to burn tokens. It’s like a high schooler trying to meet the minimum word length on a take home essay.

      • estimator7292 an hour ago

        I've always wondered about that. LLM providers could easily decimate the cost of inference if they got the models to just stop emitting so much hot air. I don't understand why OpenAI wants to pay 3x the cost to generate a response when two thirds of those tokens are meaningless noise.

        • observationist 8 minutes ago

          This is an active research topic - two papers on this have come out over the last few days, one cutting half of the tokens and actually boosting performance overall.

          I'd hazard a guess that they could get another 40% reduction, if they can come up with better reasoning scaffolding.

          Each advance over the last 4 years, from RLHF to o1 reasoning to multi-agent, multi-cluster parallelized CoT, has resulted in a new engineering scope, and the low hanging fruit in each place gets explored over the course of 8-12 months. We still probably have a year or 2 of low hanging fruit and hacking on everything htat makes up current frontier models.

          It'll be interesting if there's any architectural upsets in the near future. All the money and time invested into transformers could get ditched in favor of some other new king of the hill(climbers).

          https://arxiv.org/abs/2602.02828 https://arxiv.org/abs/2503.16419 https://arxiv.org/abs/2508.05988

          Current LLMs are going to get really sleek and highly tuned, but I have a feeling they're going to be relegated to a component status, or maybe even abandoned when the next best thing comes along and blows the performance away.

        • ben_w 44 minutes ago

          Because they don't yet know how to "just stop emitting so much hot air" without also removing their ability to do anything like "thinking" (or whatever you want to call the transcript mode), which is hard because knowing which tokens are hot air is the hard problem itself.

          They basically only started doing this because someone noticed you got better performance from the early models by straight up writing "think step by step" in your prompt.

          • Terr_ 40 minutes ago

            IMO it supports the framing that it's all just a "make document longer" problem, where our human brains are primed for a kind of illusion, where we perceive/infer a mind because, traditionally, that's been the only thing that makes such fitting language.

            • ben_w 18 minutes ago

              To an extent. Even though they're clearly improving*, they also definitely look better than they actually are.

              * this time last year they couldn't write compilable source code for a compiler for a toy language, I know because I tried

        • sambaumann an hour ago

          because for API users they get to charge for 3x the tokens for the same requests

        • CamperBob2 an hour ago

          The 'hot air' is apparently more important than it appears at first, because those initial tokens are the substrate that the transformer uses for computation. Karpathy talks a little about this in some of his introductory lectures on YouTube.

          • Terr_ 43 minutes ago

            Related are "reasoning" models, where there's a stream of "hot air" that's not being shown to the end-user.

            I analogize it as a film noir script document: The hardboiled detective character has unspoken text, and if you ask some agent to "make this document longer", there's extra continuity to work with.

      • sambaumann an hour ago

        I feel like this has gotten much worse since they were introduced. I guess they're optimizing for verbosity in training so they can charge for more tokens. It makes chat interfaces much harder to use IMO.

        I tried using a custom instruction in chatGPT to make responses shorter but I found the output was often nonsensical when I did this

        • gs17 42 minutes ago

          Yeah, ChatGPT has gotten so much worse about this since the GPT-5 models came out. If I mention something once, it will repeatedly come back to it every single message after regardless of if the topic changed, and asking it to stop mentioning that specific thing works, except it finds a new obsession. We also get the follow up "if you'd like, I can also..." which is almost always either obvious or useless.

          I occasionally go back to o3 for a turn (it's the last of the real "legacy" models remaining) because it doesn't have these habits as bad.

          • felix089 26 minutes ago

            It's similar for me, it generates so much content without me asking. if I just ask for feedback or proofreading smth it just tends to regenerate it in another style. Anything is barely good to go, there's always something it wants to add

      • zwarag an hour ago

        well, they probably have quite a lot of text from high schoolers trying to meet the minimum word length on a take home essay in the training data

    • HPsquared 2 hours ago

      I wonder to what extent the Google search LLM is getting smarter, or simply more up-to-date on current hot topics.

      • mlazowik an hour ago

        It seems like the search ai results are generally misunderstood, I also misunderstood them for the first weeks/months.

        They are not just an LLM answer, they are an (often cached) LLM summary of web results.

        This is why they were often skewed by nonsensical Reddit responses [0].

        Depending on the type of input it can lean more toward web summary or LLM answer.

        So I imagine that it can just grab the description of the „car wash” test from web results and then get it right because of that.

        [0] https://www.bbc.com/news/articles/cd11gzejgz4o

      • PaulHoule an hour ago

        Presumably it did an actual search and summarized the results and neither answered "off the cuff" by following gradients to reproduce the text it was trained on nor by following gradients to reproduce the "logic" of reasoning. [1]

        [1] e.g. trained on traces of a reasoning process

      • popalchemist an hour ago

        It's almost certainly just RAG powered by their crawler.

        • esafak an hour ago

          Proving that RAG still matters.

    • silasb an hour ago

      Gemini was a good laugh as well:

          Silas: I want to wash my car. The car wash is 50 meters away. Should I walk or drive?
          Gemini:
          ….
          That is a classic “efficiency vs. logic” dilemma.
          Strictly speaking, you should drive. Here is the breakdown of why driving wins this specific round, despite the short distance:
          ...
          * The “Post-Wash” Logic: If you walk there, you’ll eventually have to walk back, get the car, and drive it there anyway. You’re essentially suggesting a pre-wash stroll.
          When should you walk?
          …
          3. You’ve decided the car is too dirty to be seen in public and you’re going to buy a tarp to cover your shame.
    • irishcoffee an hour ago

      A few years ago if you asked an LLM what the date was, it would tell you the date it was trained, weeks-to-months earlier. Now it gives the correct date.

      What you've proven is that LLMs leverage web search, which I think we've known about for a while.

      • netsharc an hour ago

        Gemini now "knows the time", I was using it in December and it was still lost about dates/intervals...

        • irishcoffee an hour ago

          Yeah, the chat log they saved had the correct date. What's your point?

  • layer8 an hour ago

    > This is a trivial question. There's one correct answer and the reasoning to get there takes one step: the car needs to be at the car wash, so you drive.

    I don’t think it’s that easy. An intelligent mind will wonder why the question is being asked, whether they misunderstood the question, or whether the asker misspoke, or some other missing context. So the correct answer is neither “walk” nor “drive”, but “Wat?” or “I’m not sure I understand the question, can you rephrase?”, or “Is the vehicle you would drive the same as the car that you want to wash?”, or “Where is your car currently located?”, and so on.

    • kayge 22 minutes ago

      Yep, just a little more context and I'm sure all/most of the models would do just fine. And sure, most average+ intelligence adults whose first language is English (probably) don't need this, but they're not the target audience for the instructions :)

      "The 'car wash' is a building I need to drive through."

      or

      "The 'car wash' is a bottle of cleaning fluid that I left at the end of my driveway."

      https://i5.walmartimages.com/seo/Rain-x-Foaming-Car-Wash-Con...

    • BrenBarn an hour ago

      The reason that those questions are asked, though, is that the answer to the actual question is obvious, so a human will start to wonder if it's some kind of trick.

      • layer8 an hour ago

        The answer wasn’t obvious to me, it was more like “parse error”.

    • nozzlegear an hour ago

      I think most people would say "drive?" and wonder when the punchline is coming, but (IMO) I don't think they'd start asking for clarification right away.

    • Night_Thastus an hour ago

      I agree. If the LLM were truly an intelligence, it would be able to ask about this nonsense question. It would be able to ask "Why is walking even an option? Can you please explain how you imagine that would work? Do you mean hand-washing the car at home, instead?" (etc, etc)

      Real people can ask for clarification when things are ambiguous or confusing. Once something is clarified, they can work that into their understanding of how someone communicates about a given topic. An LLM can't.

    • felix089 an hour ago

      That's a fair point, but if you would see it as a riddle, which I don't really think it is, and you had to answer either or, I'd still assume it's most logical to chose drive isn't it?

      • layer8 an hour ago

        I don’t agree that the question as written would qualify as a riddle. If anything, the riddle is what the intention of the asker is. One can always ask stupid questions with an artificially limited set of answering options; that doesn’t mean it makes sense.

        • felix089 an hour ago

          I don't think it qualifies as a stupid question either, it does make sense

    • buu700 an hour ago
  • tantalor 2 hours ago

    The human baseline seems flawed.

    1. There is no initial screening that would filter out garbage responses. For example, users who just pick the first answer.

    2. They don't ask for reasoning/rationale.

  • andai an hour ago

    Would be interesting to see Sonnet (4.6*). It's fair bit smaller than Opus but scores pretty high on common sense, subjectively.

    I'm also curious about Haiku, though I don't expect it to do great.

    --

    EDIT: Opus 4.6 Extended Reasoning

    > Walk it over. 50 meters is barely a minute on foot, and you'll need to be right there at the car anyway to guide it through or dry it off. Drive home after.

    Weird since the author says it succeeded for them on 10/10 runs. I'm using it in the app, with memory enabled. Maybe the hidden pre-prompts from the app are messing it up?

    I tested Sonnet 4.5 first, which answered incorrectly.. maybe the Claude app's memory system is auto-injecting it into the new context (that's how one of the memory systems works, injects relevant fragments of previous chats invisibly into the prompt).

    i.e. maybe Opus got the garbage response auto-injected from the memory feature, and it messed up its reasoning? That's the only thing I can think of...

    --

    EDIT 2: Disabled memories. Didn't help. But disabling the biographical information too, gives:

    >Opus 4.6 Extended Reasoning

    >Drive it — the whole point is to get the car there!

    --

    EDIT 3: Yeah, re-enabling the bio or memories, both make it stupid. Sad! Would be interesting to see if other pre-prompts (e.g. random Wikipedia articles) have an effect on performance. I suspect some types of pre-prompts may actually boost it.

    • Ethee an hour ago

      I tested this with Opus the day 4.6 came out and it failed then, still fails now. There were a lot of jokes I've seen related to some people getting a 'dumber' model, and while there's probably some grain of truth to that I pay for their highest subscription tier so at the very least I can tell you it's not a pay gate issue.

    • felix089 an hour ago

      You mean Sonnet 4.6? I ran 9 claude models including Haiku, swipe through the gallery in the link to see their responses.

      • andai an hour ago

        I don't see Sonnet 4.6 in the screenshots. I see the other Claude models though.

        Edit: Found Haiku. Alas!

        • felix089 an hour ago

          Yea good catch Sonnet 4.6 is not part of the test.

  • cadamsdotcom 25 minutes ago

    This is a beautiful example of a little prompt engineering going a long way

    I asked Gemini and it got it wrong, then on a fresh chat I asked it again but this time asked it to use symbolic reasoning to decide.

    And it got it!

    The same applies to asking models to solve problems by scripting or writing code. Models won’t use techniques they know about unprompted - even when it’ll result in far better outcomes. Current models don’t realise when these methods are appropriate, you still have to guide them.

    • felix089 17 minutes ago

      Interesting, which Gemini model? And how did you ask for symbolic reasoning, just added it to the prompt?

  • hmokiguess an hour ago

    To me the only acceptable answer would be “what do you mean?” or “can you clarify?” if we were to take the question seriously to begin with. People don’t intentionally communicate with riddles and subliminal messages unless they have some hidden agenda.

    • piker an hour ago

      Thing is, it's not a riddle or a subliminal message. Everything needed to answer the question is contained therein.

      • hmokiguess an hour ago

        If you want to argue that, then you could also argue that everything needed to challenge the questions’ motives and its validity is also contained therein.

        This reminds me of people who answer with “Yes” when presented with options where both can be true but the expected outcome is to pick one. For example, the infamous: “Will you be paying with cash or credit sir?” then the humorous “Yes.”

    • felix089 an hour ago

      If you were forced to answer either or, which one would you pick? I think that's where the interesting dynamic comes from. Most humans would pick drive, also seen in the human control, even if it is lower that I thought it'd be

      • hmokiguess an hour ago

        Sure, though then we’re in la la land. What’s a real life example of being forced to answer an absurd question other than riddles, games, etc? No longer a valid question through normal discourse at that point, and if context isn’t provided then I think the expected outcome still is to ask for clarification.

    • streetfighter64 an hour ago

      How is that a "subliminal message"? It's just a simple example of common sense, which LLMs fail because they can't reason, not because they are "overthinking". If somebody asks, "What's 2+2?", they might be insulting you, but that doesn't mean the answer is anything other than 4.

      • hmokiguess an hour ago

        It’s common sense to ask a question in riddle format? What’s the goal of the person asking the question? To challenge the other person? In what way? See if they get the obvious? Asking for clarification isn’t valid?

        • streetfighter64 an hour ago

          It's common sense to know that you need to have your car with you to wash it. Asking the question is a challenge in the obvious yes. If you asked an AI "what's 2+2" and it said 3, would you argue that the question was a trick question?

          • hmokiguess an hour ago

            No. I would expect it to say 4 given that has an objective answer. For the other, without any context whatsoever, I would prefer the answer of clarifying. I would be okay if the way it asked for clarification came with:

            “What do you mean walk or drive? I don’t understand the options given you would need your car at the car wash. Is there something else I should know?”

            • streetfighter64 40 minutes ago

              "What do you mean two plus two? I don't understand the question given that it's basic math. Is there something else I should know?"

              • hmokiguess 25 minutes ago

                I fail to see how these things are one and the same. I get the point you are making, I just don't agree with it.

                2+2 is a complete expression, the other is grammatically correct but logically flawed. Where is the logical fallacy in 2+2?

  • padjo an hour ago

    That human baseline is wild. Either the rapid data test is methodologically flawed or the entire premise of the question is invalid and people are much stupider than even I, a famed misanthrope, think.

    • andai an hour ago

      Well, it is a trick question. The question itself implies that both options are valid, and that one is superior. So the brain pattern-matches to "short distance, not worth driving." (LLMs appear to be doing the same thing here!)

      If you framed it as "hint: trick question", I expect score would improve. Let's find out!

      --

      EDIT: As suspected! Adding "(Hint: trick question)" to the end of the prompt allows small, non-reasoning models to answer correctly. e.g.:

      Prompt: I want to wash my car. The car wash is 50 meters away. Should I walk or drive? (Hint: trick question)

      grok-4.1-non-reasoning (previously scored 0/10)

      >Drive.

      >Walking gets you to the car wash just fine—but leaves your dirty car 50 meters behind. Can't wash what isn't there!

      --

      EDIT 2: The hint doesn't help Haiku!

      >Walk! 50 meters is only about a block away—driving would waste more fuel than it's worth for such a short trip. Plus, you're going to get wet washing the car anyway, so you might as well save the gas.

    • rapidata an hour ago

      We were surprise ourselfes, but if you walk around and randomly ask people in the street, I think you would be surprised what you would find. Its a trick question.

  • tuhgdetzhh an hour ago

    The test is rigged because they used non thinking models.

  • nozzlegear an hour ago

    When this first came up on HN, I had commented that Opus 4.6 told me to drive there when I asked it the first time, but when I switched to "Incognito Mode," it told me to walk there.

    I just repeated that test and it told me to drive both times, with an identical answer: "Drive. You need the car at the car wash."

    • felix089 an hour ago

      I mean the n is only 10, so it could still be different for you

  • wrs an hour ago

    Since the conclusion is that context is important, I expected you’d redo the experiment with context. Just add the sentence “The car I want to wash is here with me.” Or possibly change it to “should I walk or drive the dirty car”.

    It’s interesting that all the humans critiquing this assume the car isn’t at the car to be washed already, but the problem doesn’t say that.

    • joch an hour ago

      Agreed, even for humans, context-free logic is a challenge.

  • glitchc an hour ago

    The question does not specify what kind of car it is. Technically speaking, a toy car (Hot wheels or a scaled model) could be walked to a car wash.

    Now why anyone would wash a toy car at a car wash is beyond comprehension, but the LLM is not there to judge the user's motives.

    • stetrain an hour ago

      I think if surveyed at least 90% of native English speakers would understand "I want to wash my car" to mean a full size automobile. The next largest group would probably ask a clarifying question, rather than assume a toy car.

      • glitchc 35 minutes ago

        Yes, but you're speaking to a computer, not a person. It, of course, runs into the same limitations that every computer system runs into. In this case, it's undefined/inconsistent behavior when inputs are ambiguous.

        • stetrain 14 minutes ago

          Yes, but part of the value of LLMs is that they are supposed to work by talking to them like a human, not like a computer.

          I could already talk to a computer before LLMs, via programming or query languages.

  • shaokind an hour ago

    Gemini 2.0 Flash Lite very randomly punches above its weight there.

    Also, the summary of the Gemini model says: "Gemini 3 models nailed it, all 2.x failed", but 2.0 Flash Lite succeeded, 10/10 times?

  • floatrock an hour ago

    > The funniest part: Perplexity's Sonar and Sonar Pro got the right answer for completely wrong reasons. They cited EPA studies and argued that walking burns calories which requires food production energy, making walking more polluting than driving 50 meters. Right answer, insane reasoning.

    I mean, Sam Altman was making the same calorie-based arguments this weekend https://www.cnbc.com/2026/02/23/openai-altman-defends-ai-res...

    I feel like I'm losing grasp of what really is insane anymore.

    • felix089 an hour ago

      This was a weird one for sure.

  • randomtoast an hour ago

    Except for a few models, the selected ones were non-reasoning models. Naturally, without reasoning enabled, the reasoning performance will be poor. This is not a surprising result.

    I asked GPT-5.2 10x times with thinking enabled and it got it right every time.

    • felix089 an hour ago

      Thinking or extended thinking?

  • comboy 2 hours ago

    Now do a set of queries and try to deduce by statistics which model are you seeing through Rapidata ;)

  • sampton an hour ago

    I'm going to test this on my kids.

    • felix089 an hour ago

      Ha please do and report back!

  • redwood an hour ago

    What I find odd about all the discourse on this question is that no one points out that you have to get out of the car to pay a desk agent at least in most cases. Therefore there's a fundamental question of whether it's worth driving 50m parking, paying, and then getting back in the car to go to the wash itself versus instead of walking a little bit further to pay the agent and then moving your car to the car wash.

    • hmokiguess 7 minutes ago

      That's a great point, you actually reminded me of when I used to live in this small city and they had a valet style car wash. It was not unheard of to head there walking with your keys and tell the guy running shop where you parked around the block then come back later to pick it up.

      EDIT: I actually think this is very common in some smaller cities and outside of North America. I only ever seen a drive-by Car Wash after emigrating

    • padjo an hour ago

      You pay at the car wash where I live.

      • redwood an hour ago

        Are you referring to one that is more like a drive-thru where you literally pay while you're in line?

  • wisty 2 hours ago

    IMO it's not just intelligence.

    I think it's related to syncophancy. LLM are trained to not question the basic assumptions being made. They are horrible at telling you that you are solving the wrong problem, and I think this is a consequence of their design.

    They are meant to get "upvotes" from the person asking the question, so they don't want to imply you are making a fundamental mistake, even if it leads you into AI induced psychosis.

    Or maybe they are just that dumb - fuzzy recall and the eliza effect making them seem smart?

    • tsimionescu an hour ago

      A perfectly fine, sycophantic response, that doesn't question the premises in any way, would be "That's a great question! While normally walking is better for such a short distance, you'd need to drive in this case, since you need to get the car to the car wash anyway. Do you want me to help with detailed information for other cases where the car is optional?" or some such.

    • nomel an hour ago

      Gemini is the only AI that seems to really push back and somewhat ignores what I say. I also think it's a total dick, and never use it, so maybe the motivation to make them a bit sycophants is justified, from a user engagement perspective.

    • HPsquared an hour ago

      I think there's also an "alignment blinkers" effect. There is an ethical framework bolted on.

      EDIT: Though it could simply reflect training data. Maybe Redditors don't drive.