If the title of this article made you do a double-take, don't worry. Generally speaking, it's not the driver's responsibility to change gears in an automatic car. The fact that the car can shift gears on its own is the whole reason people choose to drive an automatic transmission instead of a manual transmission or "stick shift" vehicle. So yes, most of the time, you don't have to worry about changing gears in your automatic car. However, there are a select few instances where you'll want to manually shift into lower gears (that's what the mysterious "1" and "2" on your shift lever are for) for safety and efficiency. In addition to these instances, understanding how and why automatic cars change gears when they do allows you to become a more informed and more efficient driver.
Shift Gears by Adjusting Your Speed
If you drive an automatic transmission vehicle, the internal computer automatically controls if and when the vehicle shifts to a lower or higher gear. The computer is programmed to shift gears based on the optimum RPM (revolutions per minute) for a given speed. It used to be a car feature people dreamed of seeing the in the future. Generally speaking, higher gears offer more efficient fuel consumption, but they are unstable at lower speeds and in less-than-ideal road conditions such as during a period of heavy rainfall or when there is a significant amount of snow accumulation on the road. High gears are also unreliable when climbing or descending a steep hill. Finally, shifting to a higher gear will sacrifice torque, making it much less efficient when towing any significant load, such as a trailer or a boat.
If you aren't towing anything and the roads are dry and clean, then that means it is generally safe to drive at higher gears, and you'll enjoy more economical fuel consumption as a result. To change gears in an automatic car, you must simply increase your speed. Gently press down on the gas pedal until you hear the vehicle shift—the pitch of your engine's revving will drop noticeably every time your vehicle shifts into a higher gear. As long as you don't drop below a certain speed threshold, your vehicle will remain in this higher gear until you decide to change it. Increasing your speed further can take the vehicle up into higher gears as needed.
There are not many situations where you'd want to force your car into a lower gear by this method, but for your edification, you can switch into a lower gear by doing the exact opposite of what you do to upshift. Simply take your foot off the gas pedal and allow your car to naturally slow down. Eventually, you will hear the sound of your car changing gears once again. Gently re-apply pressure to the gas pedal to maintain your speed without returning to the higher gear.
An automatic transmission vehicle does not depend solely on speed when it determines when to shift gears up or down. Acceleration and inclination also play a role. For example, if your car is set to cruise control and you approach a relatively steep hill, you will likely notice your car shifting gears in order to maintain your speed at an inclination. It is important to take note of this and other changes in your environment that may affect what gear you want to be in.
Manually Shifting Into Low Gears
If you want to change gears in an automatic car, most of the time this can be performed by simply increasing or decreasing your speed. However, there are two special low gears that actually appear on your shift lever as "1" and "2." You can switch into these gears, manual transmission style, at lower speeds in order to minimize your RPM for various purposes. You can also have fun switching gears with hilarious shift knobs.
In an automatic transmission vehicle, most driving is done with the gearshift set to "D" or "Drive," which encompasses any range of gears above about 3000 RPM. This is the setting that allows you to change gears by adjusting your speed. Just below "D" is another setting marked "2," and just below that is "1." In some cases, the lower gear or gears are designated with an "L." Most of us rarely use these settings, and young drivers may not even realize they are there, as they are rarely needed except for in a few special circumstances.
These special circumstances include towing heavy loads and going up or down a steep incline. Automatic transmissions shift gears based on the weight of your vehicle by itself, so by reducing your speed and manually switching into a low gear when you're pulling a significant load, you can ensure that your transmission is providing a high enough RPM to handle the extra weight of your vehicle. When going up a steep incline, gravity's increased affect on your vehicle affects the transmission in much the same way as if you were pulling a heavy trailer or other load. Being mindful of using a low gear when going up a steep hill is just as important as when you're towing something heavy.
Going down a steep hill is another scenario where manually downshifting is generally beneficial, but for a different reason. Rather than having to do with the proper RPM to protect your transmission, shifting into a lower gear while descending a steep incline is mainly recommended as a way to preserve your brakes. Using your brakes to descend a particularly steep road can wear them out and shorten their useful life. In extreme cases, it can even cause your brakes to overheat and fail, which is far from the ideal way to descend a hill. The risk of brake failure is particularly high if your brake pads are already near the end of their life. A good preventative measure, therefore, is to downshift into your lower gears as you descend a steep incline. You'll still need to use your brakes to slow down, of course, but shifting into these lower gears will lessen the strain your brakes endure. Make sure you still know the signs it is time to replace your brakes anyway though.
To change gears in an automatic car from "D" to "2" and "1," ease your foot off the gas pedal until you reach around 20mph. Your RPM should be at around 3000-4000, allowing you to switch into "2." Continue to slow down to as little as 10-15mph before further downshifting to "1." You can also shift directly to "1" from a full stop. Switching back out of the lower gears is the same process in reverse: when in "1," accelerate to around 3000 RPM before shifting up to "2." You'll see and hear the RPM suddenly decrease. From there, continue to accelerate until the RPM reaches around 3000 RPM again, and shift back into "D."