Which gear should an automatic transmission be in when starting the engine?

[VanCooper]

An automatic transmission should be in P (Park) when starting the engine. Here is some relevant information about automatic transmissions: 1. Automatic Principle: The engine's power is transmitted through the transmission, which is also a key factor affecting fuel consumption. Generally, automatic transmissions consume 10% more fuel than manual transmissions. Whether manual or automatic, the more gears a transmission has, the more fuel-efficient it is. 2. Driving Tips: For manual transmission vehicles, higher RPMs should be used when shifting up. Engines are designed to operate at higher RPMs, and parameters such as dynamic balance and rotational inertia of various components are also designed with high RPMs in mind. If the engine operates for long periods outside its normal working range, internal components will experience increased load and wear, leading to frequent vibrations and knocking, and reduced lifespan. Choosing 3000 RPM as the shift-up point ensures that after shifting, the engine operates at around 2300 RPM, keeping it within a healthy RPM range.

[PresleyLee]

I've been driving automatic transmission cars for over a decade, and I always make sure to put the gear in P (Park) before starting the ignition. The reason is simple: the P gear is designed to prevent the vehicle from moving. If you try to start the car in other gears like D (Drive) or R (Reverse), the vehicle might suddenly move forward or backward, which is extremely dangerous. I remember one time when a friend started the car in N (Neutral), and it shook violently—turns out it was a design incompatibility, and the repair cost a fortune afterward. Most cars only allow starting in P gear as a safety mechanism to prevent accidents. It's a good habit to always shift to P before turning off the engine, so the next time you start the car, it's ready to go—this also protects the electrical system and extends battery life. Modern car systems are smarter and won't even allow ignition in the wrong gear, but older models might permit starting in N. Still, I recommend sticking to P gear to avoid any trouble.

[DiFinley]

As a novice driver, I learned early on that ensuring the gear is in P or N before ignition is crucial. Automatic transmissions are designed to require the vehicle to be completely stable for startup, with P being the safest as it locks the gears to prevent movement. If started in a drive gear like D, engine power could cause the car to lurch forward, especially on slopes. Manuals always emphasize this—my Toyota explicitly states to start only in P. Initially, I tried starting in N; the car started but the warning light came on. A mechanic later explained it's possible but risky. For safety, make it a habit to check the gear before every ignition—don't skip that second. Consulting the manual is vital, as practices may vary by brand—American cars tend to be stricter, for example.

[LeErin]

I study automotive structures, and it's most reasonable to start an automatic transmission vehicle in the P (Park) position. Technically, the ignition circuit only unlocks the switch in P gear, preventing risks associated with starting in other gears. For example, while starting in N (Neutral) is possible, the gears aren't locked, and the car might slide on an inclined surface. The circuit design prevents power supply in D (Drive) or R (Reverse) gears to protect the starter and battery from overload. Remember to test different car brands; most Japanese cars enforce P-gear ignition, while European models might be more flexible, but experiments prove P gear is the most worry-free. With modern vehicle diagnostic systems optimized, incorrect gear selection triggers an alarm, ensuring driving safety. In short, consistently starting in P gear during daily driving extends the system's lifespan.