You just paid $3.59 per gallon for gasoline -- or something like $50 to fill up. Maybe you can save a little of that gasoline this weekend.

Shop online and have your purchase delivered in an air-friendly truck, powered by compressed natural gas. United Parcel Service is adding 21 new CNG trucks to its Fresno fleet, which already has about 100 CNG trucks.

Two-thirds of the UPS fleet in Fresno is now CNG, officials say. They say they send these trucks to Fresno because the Valley has some of the nation's worst air quality.

The advantage: CNG-powered vehicles emit 85% less NOx and 70% less reactive hydrocarbons than similar gasoline powered vehicles. NOx and the hydrocarbons create ozone, which corrodes your skin, eyes and lungs.

So, by cruising the Internet instead of Blackstone Avenue, you're saving gas money and helping air quality.