Hybrids help you save gas at the pump, this is something we all know. We also know why burning less gasoline is good: fewer greenhouse gases are emitted to the atmosphere, it reduces our dependence on foreign oil and we spend less money at the pump. However, there is always the question about what is the overall impact of using a hybrid versus using a non-hybrid version. There are currently 17 hybrid models available in the U. S. market and all but one have a corresponding non-hybrid counterpart to compare with. As part of our Earth Day coverage today, we took a closer look at the following two questions:

• Question #1: How far can we drive with a hybrid powertrain compared to a non-hybrid?
• Question #2: When will the hybrid investment pay for itself through gas savings?

Before we go to the complete list let me explain the criteria we used. First of all we chose the "economy" powertrains, when we had the option. Therefore we'll be comparing mostly 4-cylinder models. In the case of SUVs, we chose the AWD/4WD versions. For a few models, we've compared them to the European diesel versions data, although this should be taken with a pinch of salt due to the EU's different driving cycles. Finally, we used $3.5/gal as the price of gasoline and added the car's MRSP price. Don't forget that some of these vehicles will qualify for various tax breaks, so you might have to recalculate our numbers for yourself. Got all that? Good, let's see the results (after the jump).

Those Dagenham windmills. The Fumes to Fuel paint project. Renewable energy at the Cologne plant. Much of what Ford is touting in its Earth Day press release (read it yourself after the break) is old news to us on AutoblogGreen. If you're interested in the broad sweep of what Ford is trying to do around the world to reduce its impact on the environment, the release is a great place to start. It's not a bad idea to review those changes, as Ford's efforts have had quite an impact. According to the company, when all global operations are taken into consideration, CO₂ emissions are down by 39 percent, water usage dropped by 43 percent and total energy use is 30 percent lower (compared to 2000 numbers). That's mighty impressive. Now, if every factory were zero-waste like Subaru's Indiana facility, we'd really be making progress.

With the arrival of spring, many of us have been busy preparing our gardens for the upcoming growing season. The soil needs to be tilled, fertilized and well hoed to ensure a bumper crop. And speaking of bumpers, the folks over at AFS Trinity have been polishing theirs (you see what I did right there?), getting ready for an epic cross country trip from the gritty streets of San Francisco to the gleaming metropolis of Washington. With their D.C. arrival to correspond with that of Earth Day, they have hopes of finding some politicians on the Capitol Mall in search of a good green-tech photo-op with their XH-150. One thing is certain, with a gas hitting $4.00 a gallon in some places, the semi hauling their hi-tech hybrid, with a glossy picture of an SUV and "150 miles per gallon" in big letters should get them lots of attention from the gathered masses.

Since they have two weeks to complete the journey, there are plans for several stops along the way. There will be a detour through Austin, TX to give a demonstration of their miracle machine to municipal utility, Austin Energy as well as Plug-in Partners, "a consortium of electric utilities and others supporting the development and introduction of new plug-in hybrid electric vehicle (PHEV) technologies", according to a press release published at The Earth Times. There will even be an opportunity for a select few to take their 40 mile PHEV SUV FATD (for a test drive) in one of several communities along the way. We wish them a bon voyage and await their invitation. See pictures of XH-150 and the billboard disguised as a semi-truck in the gallery below. Hit the jump for a press release full of details and remember that the way AFS Trinity defines "150 mpg" is slightly skewed.