McLEAN, Va. -

Though diesel vehicles might not be considered environmentally friendly by all, the bottom line is, they are more fuel-efficient than there gasoline counterparts.

And as fuel efficiency becomes more and more of a concern for shoppers, the Environmental Protection Agency said that diesel vehicles are making a bit of a comeback in the U.S. after years of poor sales and meagre product offerings.

Analysis from NADA Used Car Guide suggests that although diesel rides are some of the most efficient on the market, their high price tags can be a bit of a determent.

“While diesels are more fuel efficient and generally earn higher used retention scores, costs can be substantially more up front, and the widening spread between diesel and gasoline prices — which went from 11 cents in 2009 to 42 cents in 2013 — mean that fuel savings may not be as great as they once were,”  theNADA UCG analysis indicates.

To determine whether diesel vehicles are worth the higher premium, NADA UCG compared two different 3-year-old vehicles and their respective diesel counterparts: the Volkswagen Jetta and Mercedes-Benz ML350.

Analysts looked at each model’s combined MPG, new typically equipped MSRP, April 2014 average trade-in value and retention after three years of ownership versus similarly equipped gasoline models.

They came up with a few points that may point toward stronger diesel sales in the future.

First, when NADA UCG examined  the diesel Jetta and ML350, the models beat out their gasoline counterparts in every category except for carrying higher new equipped MSRPs.

“While each diesel model was more expensive up front, the extra outlay of money appears to be well worth it after three years of depreciation,” NADA UCG reported.

For example, the Jetta was $3,584 more expensive than the gasoline version. But there’s a caveat.

According to NADA UCG’s Average Trade-in Values from April, the gap between values has expanded to $3,925 in favor of the diesel.

NADA UCG found that retention was stronger among the diesel models. The Jetta TDI retained 60.1 percent of its original value after three years of depreciation, while the gasoline-only SE model retained 51.6 percent.

The same situation was found for the ML350. When new, the diesel version costs $910 more than a similarly equipped gasoline model, but current trade-in values show that this spread has increased to $3,400 in favor of the diesel.

After three years, the ML350 BlueTEC 4MATIC retained 52.3 percent of its original value, while the gasoline-only ML350 4MATIC has retained 47.1 percent.

Another argument many use as a deterrent to diesel vehicles is the higher cost of diesel fuel.

But, in light of the fuel efficiency of some of these models, that isn’t so much of an issue.

The Jetta TDI annual fuel savings came in at $217, and the ML350 Blue TEC saves shoppers $571 a year, according to NADA UCG data.

These calculations were found when looking at average 2013 fuel cost associated with each model when driven 15,000 miles.