A late-March protest by US truckers fizzled. Hoping to call attention to crushing increases in diesel prices, independent truckers at the end of March drove slowly to disrupt traffic in several areas and talked about a strike. For the most part, traffic and business proceeded normally. And the national average diesel price loitered just below $4/gal. Do beleaguered truckers know diesel doesn’t have to be this pricey yet may become even more so?Crude prices above $100/bbl largely explain recent spurts in prices of diesel and other oil products, of course. But they don’t explain why diesel has come to sell at a stout premium to gasoline most of the time instead of the discount t...