Most of the time, burning oil is a bad thing; think of thick, dark smoke pouring out of a truck's exhaust pipe as it tools down the highway. But thanks to a Pennsylvania company called Clean Burn, burning oil can save companies money while they do their bit for the environment.

Clean Burn's equipment allows users to recycle used motor oil, burning it in a special furnace to heat small buildings. Customers, which include a number of for-hire and private truck fleets, say the furnaces save them thousands of dollars on energy and used-oil disposal costs. The fleet maintenance manager of a construction company with a large fleet of heavy-duty trucks and road equipment saved $28,000 in just three months by eliminating waste disposal and using the furnace to heat a 13,000-square-foot maintenance facility.

To learn more about heat recovery from used motor oil, go to www.cleanburn.com.