Garmin's ecoRoute saves on gas, but maybe not time

We're used to GPS car units telling us where to go.

Now they also have the ability to urge us to be more eco-friendly drivers.

Garmin International Inc., one of the leaders in global positioning systems, has added a function called ecoRoute to many of its car navigation devices.

It also can be downloaded free and added to some existing units (for a list of models that can use the feature, go to www.garmin.com/ecoroute and click on "Compatible Devices").

EcoRoute is designed to track your driving style with satellite signals in order to "calculate your vehicle's fuel economy, carbon footprint and fuel price of navigating to a destination," according to its online manual.

It also offers "fuel-saving tips," the company says.

So, would this be a handy way for drivers without built-in fuel calculators -- which come on Prius hybrids and some other car models -- to add this function?

Or would it be more like having a grumpy Al Gore in the passenger seat?

I took ecoRoute on a spin to find out.

Normally, the Garmin gives you route calculation choices that include "Fastest Time" (the default selection) and "Shortest Distance." EcoRoute adds a "Less Fuel" choice.

To test it, I first plotted a trip to my local dry cleaner based on the usual "Fastest Time." The GPS (Garmin's 265WT model) came up with a surface-street route that required only three turns.

Switching to the "Less Fuel" selection, the unit mysteriously came up with a longer route that required seven turns, including some onto streets I'd never heard of.

I took this route, which was kind of nice because I got to see parts of my neighborhood I'd never driven through before.

But was this really saving gas and pumping less contaminants into the atmosphere?

The route even included a left turn on a busy boulevard that left me at a stop sign for a couple of extra minutes, burning fuel.

The next test was from a park in Pasadena to a sporting goods store, which would have been an easy hop on the freeway.

But "Less Fuel" included no freeway driving.

Finally came a trip through the northern San Gabriel Valley to a big-box membership store. Again, no freeway driving on the "Less Fuel" route, which mainly used busy Foothill Boulevard.

As I drove along haltingly (because of traffic and numerous stoplights) I came to think of ecoRoute as a kind of time machine, taking me back to an earlier era when almost all driving was on surface streets.