It's almost hard to believe today in the United States, but decades ago a significant percentage of Mercedes-Benz vehicles sold here ran on diesel fuel. With diesel currently more expensive than premium gasoline in many places now, and Mercedes diesels having helped ruin their own reputation as time progressed, diesel has a long way to go. Even today, in many people's minds there's still a negative stigma of slow, clattering, stinking diesel W123s with the rear end blackened with soot. In today's era of modern clean-running diesels, that's not as much of a problem. They're also inherently more fuel-efficient than many gas-powered engines, so in many cases a diesel can be a smart buy if its fuel economy offsets the increased fuel cost per gallon.