The engine in the LC is tuned slightly differently than the same engine in the Grand Highlander and Tacoma. My guess is that Toyota is running a slightly higher boost from the turbo which necessitates the higher octane gas to prevent engine knock. Engine knock can be caused by the pre-ignition of the fuel in the cylinder (meaning that the fuel/air mixture has ignited earlier than ideal.) Modern engines like the one in our LC have many sensors, including knock sensors, so you might be able to run a lower octane fuel without experiencing the detrimental effects of engine knock. That doesn't mean it's a good idea! Mazda makes a straight 6 for the CX-90/CX-70 that accepts either 87 or 91 octane. Running the 91 octane improves the performance of the engine (more HP and more torque), but you can safely run 87 octane because the engine can adjust its tuning for the lower octane. Given that Toyota doesn't give this option, it's possible that the engine tuning may not safely accommodate using lower octane fuel. Just because you can run 87, doesn't mean you should.