NEW YORK (MainStreet) – Pickup trucks, vans, crossovers and SUVs are more efficient than they once were, but that isn't saying much.

Vehicle fuel efficiency standards are inching toward the Environmental Protection Agency's goal for company fleet averages to hit 54.5 miles per gallon by 2025, but at a pace that makes Friday rush hour look like the Monaco Grand Prix. Muscly pony cars like the Ford Mustang, Chevrolet Camaro and Dodge Challenger all get 30 miles per gallon on the highway out of their most fuel-efficient versions. Tesla considers its Model S a performance car and it doesn't use a drop of fuel to cover its 270-mile range.

The University of Michigan Transportation Research Institute found that cars and light trucks purchased in 2014 got an average of 25.4 miles to the gallon. That's still less than halfway to the EPA and Department of Transportation's goal that it set back in 2012, but it beats the roughly 19 miles per gallon that the Department of Transportation measured for the same pool of vehicles in 1995. It's also closing in on double the average mileage of the light-duty vehicles on U.S. roads in 1980.

That said, there are still a lot of cars out there getting terrible mileage. That doesn't include the supercars that the EPA ranks among the least-efficient cars sold in this country. However, the problem is that the average U.S. car buyer isn't picking up a Bentley Mulsanne (13 mpg), Ferrari FF (also 13 mpg) or a Bugatti Veyron (10 mpg). In fact, Bentley and Ferrari combined accounted for fewer than 2,000 of the more than 7 million cars sold in the U.S. through June according to MotorIntelligence.

Also, despite strides made by lighter pickups and smaller crossover SUVs within the last decade or so, the fuel efficiency of those vehicles still isn't all it could be. Fuel prices that have dropped nearly 90 cents per gallon since this time last year have increased pickup sales 10% through June. They've also boosted sales of SUVs 12.6% during that span. In that mix are some of the EPA's worst mileage offenders. The following five vehicles are such huge gas guzzlers that a gallon of gas will hardly get you 20 miles out of any of them:

Passenger van: Chevrolet Express 3500 Passenger

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Starting price: $32,190

EPA combined city and highway mileage: 12 mpg

This is the last of the old, round, bulky, all-purpose U.S. vans. Ford abandoned its econoline for the more European stylings (and efficiency) of the Transit in an attempt to keep pace with Mercedes-Benz's popular Sprinter line. Unfortunately, Chevrolet hasn't taken that cue and sticks with a van that looks as if it was built explicitly for church youth group outings and senior center shuttle service. At a paltry 12 miles per gallon, it's woefully short of even the Transit's combined 17 miles per gallon and serves as a relic of an era when a passenger van's most frequent destination was the gas station.

Cargo van: GMC Savana 2500 Conversion

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Starting price: $29,555

EPA combined city and highway mileage: 12 mpg

This is the Chevrolet Express's sibling, but it's likely more recognizable to the layman as the van you pulled off the rental lot that weekend you had to move a sofa and about five IKEA bookshelves from your friend's apartment. Nearly naked without its U-Haul or Penske graphics, the Savana's key frills are available Wi-Fi and easy-to-read instruments. GMC knows this is a contractor's truck or a service vehicle at best, but it also knows it's offering one of the last options in town for a cargo van. In fact, while the Savana has the worst mileage of any cargo van the EPA tested, it also has the best -- which should tell you exactly how little pressure General Motors is feeling to trim the mileage on this monster.

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Small SUV: Nissan Xterra

Starting price: $23,660

EPA combined city and highway mileage: 19 mpg

Sure, a four-wheel-drive version takes the 19 mpg number down to 17 mpg. But this old-school truck-platform SUV hasn't received an update since 2009 and is being discontinued after 2015 amid declining sales. The standard midsize SUV saw sales increase 17% over the last six months from the same period in 2014, but the 390,000 sold are still a fraction of the 1.7 million car-based crossover SUVs sold during the same period. Nissan has no plans to replace the Xterra or to produce another SUV for off-roaders (who basically justified the Xterra's existence). A look at the 30 mpg combined mileage of Nissan's Rogue crossover provides at least some explanation.

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Minivan: Toyota Sienna

Starting price: $28,600

Combined city and highway mileage: 21 miles per gallon

Toyota, the “swagger wagon” branding isn't working. It's a minivan. It's the greatest parental aid since bribery. It's an eight-passenger, modular-seated, power liftgate-enabled, Blu-ray-playing school shuttle and grocery getter. Yes, it has a 3.5-liter V6 engine, but that power is used primarily to pull onto the highway on the first leg of a family vacation. There's a lot of great safety and entertainment technology in the Sienna, as well as an all-wheel-drive option that drops combined mileage to 19 mpg, but none of it makes this fairly inefficient vehicle a party bus. It's the family car, and pretending it's a bulletproof luxury SUV while pulling it into the valet lane isn't going to get you anything other than a few chuckles.

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Full-size SUV: Mercedes-Benz G550

Starting price: $114,400

Combined city and highway mileage: 13.5 miles per gallon

No, it isn't the most populist of SUVs, but it's out there. It's a member of a luxury SUV class that has watched sales soar 26% this year, and it doesn't apologize for being terrible at the pump.

If you're buying a G550, chances are you're paying more attention to the 5.5-liter V8 engine, the 382 horsepower, the 7,000-pound towing capacity, the off-road features, the driver-assisting technology, the Nappa leather seats, the privacy glass and the touchscreen entertainment system. The cost of gas is clearly someone else's concern and a small line item among your annual expenditures.

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Small pickup truck: Nissan Frontier

Starting price: $17,990

Combined city and highway mileage: 21 miles per gallon

Granted, both the Frontier and the Toyota Tacoma's four-wheel-drive versions get a paltry 17 miles per gallon combined, but the Tacoma's standard combined mileage of 23 miles per gallon keeps it out of this doghouse.

Known as the Nissan Navara in Europe and not sold in Japan at all, the Mississippi-made Frontier just continues the mileage losing streak for Nissan. Unlike many of the Nissans named here, however, the Frontier doesn't exactly have a replacement in the pipeline. Nissan released a next-generation Navara throughout the rest of the world last year, but insists the Thailand-produced vehicle isn't indicative of the Frontier's replacement. What is apparent, however, is that Nissan is putting its worst foot forward in a truck category that the Ford Ranger abandoned and that the Chevrolet Colorado only recently reentered.

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Full-size pickup truck: Nissan Titan

Starting price: $29,640

Combined city and highway mileage: 15.5 miles per gallon

It's as if Nissan forgot pickups were vehicles U.S. drivers liked. The company has gone back and forth over redesigning this full-size pickup since it was released in 2013 and watched U.S. sales sputter from 85,945 in 2005 to just 12,527 last year -- with roughly a quarter of those sales taking place in Texas alone. The fully updated 2016 Titan will be made solely in the U.S. for North American buyers and will have a 5.0-liter, 310-horsepower V8 Cummins engine that truck owners will love, but the current Titan's terrible gas mileage, which drops to 14.5 mpg in the four-wheel-drive version, is just one of the many features that have made U.S. buyers indifferent to it.

This article is commentary by an independent contributor. At the time of publication, the author held TK positions in the stocks mentioned.