I think diesel will come down, just slower and it may not be cheaper than gas.
Bob Hegbloom, head of the Ram brand, said that the widening diesel-gasoline price gap hasn't softened demand for the brand's hot-selling light-duty diesel pickup.
"We're still seeing fantastic sales numbers," Hegbloom said.
But he conceded: "It's a tough time to ask that question. December is the largest month of the year for truck sales."
Hegbloom said consumers have waited so long for a light-duty diesel that there's probably some pent-up demand that Ram is working through. In September, the brand said it was increasing the EcoDiesel production mix to 20 percent of all Ram 1500s.
Gutierrez said the fuel price gap mostly affects the car market, in which buyers are more likely to base their math on fuel savings. At current prices, that math doesn't work in diesel's favor.