It has been around a week since Tesla (TSLA) began the rollout of FSD v12.5 to the legacy Hardware 3 (HW3) cars. The automaker started this deployment from version 12.5.1.5 of its Full Self-Driving Supervised software.
The original early access (OG) FSD beta tester, AI DRIVR/YouTube, shared his experience driving FSD v12.5.1.5 in busy parking lots and city streets (see below). He tested this version on an HW3 2018 Tesla Model S car.
The interesting thing about this test is that the beta tester was able to compare the performance of FSD 12.5 on both HW4 and HW3 cars. He has previously driven FSD v12.5 on his newer HW4 Tesla Model S.
Although @AI DRIVR shared his first impressions of FSD v12.5.1.5 on his HW3 Tesla Model S earlier, he didn’t post a video of an exhaustive test in different scenarios.
As of this writing, 860 out of 20,099 data-contributing Tesla cars have been migrated to FSD v12.5.1.5. The majority of HW3 cars are still running on the old FSD v12.3.6 (source: TeslaFi.com tracking website).
FSD v12.5: HW3 vs HW4
Last week, Tesla AI Director Ashok Elluswamy explained that the software model of FSD 12.5 had to be reduced to work on the legacy HW3 computer cars to work optimally. AI DRIVR shows us how it performs in real-world scenarios.
According to the tester, FSD v12.5 outputs the same performance handling traffic situations on HW3 as it does on HW4 cars. However, we used the word ‘almost’ in the article title to show that it does not work identically. There are some areas where FSD v12.5 demonstrates its limitations. This can be the result of both the limited hardware capability of HW3 compared to HW4 and also due to the software optimization also noted earlier by Tesla CEO Elon Musk.
According to AI DRIVR (a previous Tesla employee as well), except in some scenarios, FSD 12.5 on HW3 Tesla vehicles performs as good as it does on HW4 cars.
Driving Visualizations
The instrument cluster of the 2018 Tesla Model S does show some flickering and visual issues rendering the FSD 12.5 driving visualizations. With the recent more advanced FSD versions, Tesla cars have been observed to compute objects and situations that aren’t necessarily displayed in the visualizations. With limited capability on HW3 cars and older media control units (MCUs), visualizations shouldn’t be expected as good as on the newer-generation Tesla cars running on HW4 and the new AMD Ryzen-based MCUs.
Random Slowdowns
Another major observation during the test of FSD v12.5.1.5 on the HW3 Tesla Model S was random slowdowns. AI DRIVR observed that HW3 cars still experience more random slowdowns on FSD 12.5 compared to HW4 vehicles where this phenomenon is a rare occurrence now.
In the test video below, we can see that the HW3 Tesla car slows down abruptly while crossing an intersection. There wasn’t any traffic around but the vehicle probably got over-cautious and slowed down very close to the intersection which isn’t an ideal behavior I guess.
Various Scenarios and Disengagements
FSD v12.5 on HW3 in this test performed very well on a roundabout. According to the tester, the same car with the older FSD Supervised versions struggled this roundabout. This time, it took the right lane and maintained a good follow-distance. AI DRIVR noted that the FSD v12.5 running on HW3 feels like more human than a robot driving the Tesla vehicle.
Driving on busy streets, the HW3 Tesla Model S also drove more naturally after the FSD v12.5.1.5 update. It handled lane lines like we humans do, sometimes ignoring them when needed to take the smoothest path possible.
However, the vehicle got confused on a street when a driver was parking his vehicle in the driveway. As soon as the other car moved forward, the HW3 Tesla tried to move forward. Tesla driver disengaged Autopilot to take control of the vehicle. This was the only safety disengagement/human interruption in the entire test.
Compared to the older versions running on HW3, such as FSD v12.3.6 — the performance has a “night and day” difference, says AI DRIVR.
Stay tuned for constant Tesla updates, follow us on:
Google News | Flipboard | X (Twitter) | WhatsApp Channel | RSS (Feedly).
Related Autopilot/FSD News
- Musk promises a $30K or less Cybercab delivery before 2027, Tesla (TSLA) produces the first unit at Giga Texas
- Outright purchase of Tesla FSD is still available for the Model S and X (Luxe Package), and the Cyberbeast
- Tesla update 2026.2.3: hidden features, Service Mode FSD updates, battery recalibration, more
- Lemonade offers 50% insurance discount for Tesla owners using the safer Full Self-Driving (FSD)
- Watch Tesla FSD give way to an ambulance before the human driver could even hear it
- Tesla expands the rollout of FSD v14.2.2.4 (2025.45.9), release notes and first impression videos
