Car Talk: There's no harm in keeping your car in eco mode

Good question, Don. It doesn’t do any harm at all. Engines and transmissions are all controlled by computers now. So, for instance, the point at which your transmission shifts is determined by what code gets programmed into the transmission computer.

Well, since it’s so easy to change, most cars now come with multiple sets of parameters for the engine and transmission. And you get to select which one you want.

Generally speaking, those settings change when the transmission shifts and with how quickly the engine responds to the gas pedal. Most new cars these days have some combination of eco, normal (sometimes called comfort) and sport.

Normal is the default setting. That’s what the engineers think most people will prefer. Normal balances fuel economy with reasonable performance.

Eco tries to maximize fuel economy by lowering the transmission shift points (making the transmission shift sooner) and sometimes making the gas pedal slower to respond.

Sport does the opposite. It raises the shift points and prioritizes acceleration over fuel economy.

None of these settings are harmful, Don. And, in fact, eco might be the most beneficial in the long run, since it leads you to drive more gently.

So, why don’t manufacturers just set the car in eco permanently? Because they’re afraid nobody would buy it.

While some people take great pleasure in saving fuel and money, there are apparently more people who take greater pleasure in beating the Nissan Sentra in the next lane when the light turns green.

And if a car is only modestly powered to begin with, it will often seem underpowered in eco mode. At least to an important fraction of drivers.

But you can use it to your heart’s content, Don. You’re doing good things for your car, the environment and your wallet. Not to mention your index finger strength — from having to push the eco button every time you drive.