Dear Car Talk:
I drive a 2005 Subaru Outback and live in a very lovely and hilly town. My Outback has an automatic transmission. When I'm stopped at a red light facing uphill, I sometimes hold the car by lightly touching the accelerator. Sometimes I use the brake pedal. When I do use the brake pedal, the car will roll back slightly before the transmission can grab on and move the car forward. Which method of holding the car on a hill is less detrimental to the transmission? To hold or brake ... that is the question. Thanks. -- Fritz
That's the question, Fritz. And the answer is: It hardly matters.
Automatic transmissions are designed to "slip" when you come to a stop. If they didn't slip, the engine would stall, just like it would if you were driving a car with a manual transmission and came to a stop while still in gear.
So, slippage -- with automatic transmission fluid absorbing the power of the engine and turning it into heat -- is just part of life when you're an automatic transmission. And from the transmission's point of view, there's not a great deal of difference between slipping a little bit while holding the car on a hill and slipping a little bit more, for a shorter time, when you roll backward and need to change direction.
If those were my only two choices, I'd probably choose to let it roll back. But fortunately, those are not your only choices, because they both have downsides. If you use the gas pedal to hold the car on a hill, you probably have to rev the engine up to 1,500 rpm or more to stay in place. If you do that frequently, you're wasting a lot of gas. And if you use the "roll back and then go forward" approach, if the hill is steep enough, you could roll back right into the grille of your local mob boss's brand-new Lincoln Continental.
So your best bet, since this is an everyday occurrence for you, is Option 3: Learn to use your handbrake while waiting for the light to change. When you arrive at a light, pull up the handbrake, and let the handbrake hold the car in place. If there's traffic behind you and you want to be "ready to go," you can even hang on to it, with the release button engaged while you wait. And when the light turns green, just release the handbrake as you step on the gas, and you won't roll backward.
For those who don't have a pull-up hand brake like Fritz's Outback does, you can accomplish the same thing by "two-footing it": Use your left foot to hold the brake pedal while you wait, and then ease off it as you step on the gas.
Problem solved! And now that we've eliminated this existential source of worry for you, Fritz, we hope you'll have more time to contemplate some truly important things -- like global warming, net neutrality and who Jon Snow's mother is on "Game of Thrones."