EFFERSON CITY, Mo. -- The National Biodiesel Board is advising commercial vehicle operators to buy biodiesel only from a trusted source because theres generally no easy-to-spot, at-the-pump certification.

The trade group also issued the following recommendations for buying B20 blend biodiesel:

Buy fuel that is already blended. This will help assure the fuel has been properly handled and treated for climatic needs.

Biodiesel is a cleaning agent, which means petroleum deposits may end up in the fuel filter until the vehicle fuel system is clean. Stick to your regular maintenance schedule unless your vehicle feels sluggish when accelerating. This is a symptom of a plugged fuel filter and should be checked immediately.

Never buy from someone making biofuel in a garage or backyard.

The board recommends that interested fleet operators check the list of registered marketers at www.biotrucker.com, or by calling (866) 246-3437.

Meanwhile, all diesel fuel sold in Portland, Ore., will be required to contain at least 5 percent biodiesel beginning July 1.

The standard applies to fuel sold in Portland for use by on-road vehicles. It does not apply to diesel sold in Portland and subsequently transported outside the city.

In 2010, the biodiesel requirement will increase to 10 percent.

The new standard also requires that all gasoline sold in the city contain at least 10 percent ethanol by Nov. 1.

Earlier this year, the Oregon House approved a bill that included a requirement that at least a 2-percent biodiesel blend be offered as soon as state production of biodiesel reaches 5 million gallons per year. (See May 1 Bus & Motorcoach News.)