Here's why:
* Zero tolerance engines are designed with extremely tight tolerances between moving parts, requiring the use of special assembly techniques and extremely precise machining. They are typically found in high-performance racing engines, not in standard production cars.
* The 3FSE, while a relatively high-performance engine for its time, was a standard production engine. It was designed for reliability and durability, not for maximum performance.
* Standard production engines like the 3FSE are designed with a reasonable tolerance range for normal wear and tear.
Therefore, while the 3FSE engine is known for its robustness and longevity, it's not considered a zero-tolerance engine.
