Yes they can depending on what regulations there are on biodiesel labeling in your state. In CA I think yhey have to state the blend percentage. On the bright side you still get lubricity benifits at 2%.

Stephen

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85 300D 305K miles WVO(105K so far), Mine
82 300SD 235K miles BIO-D, Wifes
96 F250 SC PSD 4X4 285K MILES BIO-D, Ours
89 BRONCO 182K MILES sold
Finally Compression Ignition Only!