AFP/Getty Images U.S. diesel prices at the pump could climb to well over $4 a gallon next year, says Tom Kloza of OPIS.Prices for diesel fuel may revisit record highs within the next year or two, affecting many markets—from refiners to transportation to agriculture. U.S. diesel prices at the pump stood at $3.167 a gallon on Friday, according to data compiled by the Oil Price Information Service, or OPIS, for motoring and leisure-travel group AAA. They averaged $3.09 a gallon this month, the highest monthly level since December 2014. “Prosperity in the global economy comes with a price, and it can really manifest itself in diesel or jet fuel prices,” says Tom Kloza, global head of energy analysis at OPIS. But a demand boost from a strong economy isn’t the only reason for the 3½-year high in diesel prices. The fuel is refined from crude oil, and prices for crude have also recently climbed to their highest levels since late 2014. “As crude-oil prices increase…diesel prices will, too,” says Jeff Klearman, portfolio manager at exchange-traded funds issuer GraniteShares.via