Luxury was briefly where the future of automobile efficiency lived.

That's no longer the case. With the Tesla Model 3 starting at $35,000, the $37,500 Chevrolet Bolt electric vehicle hitting showrooms next year and mid-level electric and hybrid vehicles becoming more accessible as infrastructure improves, efficiency is no longer solely the domain of high-end vehicles.

That isn't necessarily a bad thing. Even with gas prices finally creeping up above $2 per gallon again, according to AAA, there's still a need for the vehicle pool as a whole to get more efficient. The Environmental Protection Agency's goal of a fleet-wide combined 54.5 miles per gallon by 2025 is still on the table. The University of Michigan Transportation Research Institute found that cars and light trucks purchased in 2015 got an average of 25.3 miles to the gallon, which is actually 0.1 miles per gallon less efficient than they were in 2014.

Of the roughly vehicles identified as luxury sedans by the EPA between the 2016 and 2017 model years, roughly 18 manage more than 25 miles per gallon combined. That is also worse than last year, when about two dozen vehicles hit that mark.

High-end luxury vehicles including the Bentley Mulsanne (just 14.5 miles per gallon combined), the Rolls-Royce Phantom (15 mpg), the Mercedes-Benz Maybach S 600 (16.5 mpg) and Maserati GranTurismo (17 mpg) aren't helping. However, even somewhat downmarket options like the Mercedes-Benz CLS500 (25 mpg) and BMW 328i (25 mpg) aren't thriftier with their fuel.

This isn't great news for luxury automakers, who've seen luxury sedan sales slump 13.8% year-to-date, according to MotorIntelligence. While cost will always keep the luxury sector's 231,000 cars sold through March a small percentage of the 1.7 million cars sold in the U.S. during that time, buying patterns aren't working in their favor.

Through March, Bentley down (51%), Alfa Romeo (down 22%), BMW (down 10% overall, but 26% among cars), Porsche (down 13% among cars), Mercedes-Benz (down 17.2% on cars), Audi (down 5.7% on cars) and Volvo (down 43% on cars) have all seen non-SUV/crossover sales plummet amid falling gas prices. Yet Tesla's car sales are up 70%.

Big changes are coming to the luxury sedan market, and a bunch of automakers are really struggling with it. With help from the EPA's, we deveoped a list of the most fuel-efficient luxury sedans on the market. Though on the EPA's list, the BMW i3 didn't make the cut because, because it isn't really a sedan. That said, its efficiency may have owners wishing it was one:

10. 2016 Cadillac CT6

MSRP: $53,495

Miles per gallon: 26.5 combined

Hey, Cadillac is finally joining just about every other luxury automaker in embracing the letters-and-numbers naming convention. Fortunately, it didn't throw out its opulent features with its old-money monikers.

Making its debut this year, the lightweight CT6 with its 3-liter V6 twin turbo engine is the most efficient vehicle in Cadillac's lineup. Wood trim is woven into carbon fiber, gauges are replaced with an all digital interior including a massive 10.2-inch touchscreen and the exterior is monitored with pedestrian warning signals, enhanced night vision and wraparound camera views of all portions of the car.

The Cadillac CUE infotainment system supports Android Auto and Apple CarPlay and features a separate screen for rear passengers -- as well as hands-free texting for the driver. Perhaps the most impressive option is the Bose Panaray sound system that features a whopping 34 speakers, individual climate control and extended comfort seats with five massage settings. This is about the least “Cadillac” a Cadillac has been, and it's a huge step into the future for everybody's grandparents' favorite brand.

9. 2016 BMW 528i

MSRP: $50,200

Miles per gallon: 28.5 combined

The 2.0-liter 4-cylinder engine and its 240 horsepower are underpowered for a BMW, sure, but that isn't the purpose of a vehicle this efficient.

The hybrid-style brake energy regeneration system powering Xenon headlights, LED accent and fog lights, LCD displays, automatic dual-zone climate control, ten-speaker stereo system and moonroof are your selling points. The leather steering wheel, dark wood trim, BMW Navigation and iDrive system with touchpad controller just make it a bit more plush. Along with that emblem on the hood, that's what most 5 Series drivers are looking for.

8. 2016 Audi A6/A7 quattro

MSRP: $46,200 and $68,300

Miles per gallon: 29.5 combined

Yep, just different sizes of the same diesel-driven car.

The options don't really change much until you get to the more luxurious A8. Both vehicles get the access to the same features, including the Style package (xenon headlights and 18-inch wheels), the Innovation package (includes head-up display and night vision assistant), the Cold Weather package (heated front and rear seats and heated steering wheel), the Sport package (adds a sport-tuned suspension, a sport steering wheel, shift paddles and either 19-inch wheels with all-season tires or 20-inch wheels with summer tires), the Driver Assistance package (top-view camera system with front and rear corner views, adaptive cruise control, active lane assist and the Audi Pre-Sense Plus collision mitigation system) and the Black Optic package (available with the Sport package, and adds 20-inch wheels, summer tires and high-gloss black trim).

Audi still knows how to load up a car, so it's up to you how much Audi you'd like to squeeze into.

7. 2016 BMW 535d

MSRP: $57,350

Miles per gallon: 31.5 combined

Hey, the BMW diesel made the cut! The 535 just received its diesel version in 2014, but BMW loaded it up with a standard navigation system, leather upholstery, adjustable driving settings (which alter suspension, steering, throttle and automatic transmission response), adaptive bi-xenon headlights, automatic wipers, heated mirrors, a sunroof, auto-dimming mirrors and keyless ignition/entry. Its diesel system got some scrutiny overseas, but it's fared just fine here.

Besides, the dual-zone automatic climate control, dark wood trim, ambient lighting, ten-way power front seats, driver memory functions, split-folding rear seats, BMW Assist emergency communications system and the iDrive electronics interface (with smartphone app integration) serve as nice rewards for your faith in it. A Premium upgrade includes includes a hands-free power trunk lid that opens or closes automatically when you swipe your foot under the rear bumper while holding the remote, keyless access to all doors and satellite radio.

6. 2016 Lexus GS 450h

MSRP: $63,080

Miles per gallon: 31.5 combined

Yes, Toyota managed to make the CT200h hybrid look like a fancy Prius, but the GS doesn't make that mistake by trying to spruce up the Camry. A sporty 306- to 336-horsepower hybrid with paddle shifters and a tachometer still appeals to the tuners, but the toys set this apart.

A giant 12.3-inch display for navigation, audio and climate controls to voice command, a 17-speaker sound system, Bluetooth connectivity and the Lexus Enform information and entertainment app system are some impressive, standard distration. However, comforts including heated and ventilated seats, 18-way power front seats, rear-seat audio and climate controls, a driver attention monitor that makes sure you aren't drifting and all-wheel drive that keeps you steady on slick roads are particularly cushy for a hybrid.

5. 2016 Mercedes Benz E250 Bluetec diesel

MSRP: $52,650

Miles per gallon: 35 combined

Yeah, we'll admit that the term “clean diesel” had a rough ride last year. While that wasn't great for Volkswagen, Audi or even BMW, Mercedes managed to come through on its promises here in the U.S. Besides, an emergency monitoring service, a driver-fatigue monitor, pre-collision automatic braking, blind-spot detection and a lane-departure warning system should make you feel secure in the car, if not in the clean-diesel technology.

The Mercedes engine and handling make the driver feel give it the feel of a racer, while the four-seater's COMAND entertainment, navigation and communication system, dual-zone automatic climate control, ventilated seats and rear DVD entertainment system keep everyone else entertained while the driver hugs the turns.

4. 2016 Porsche Panamera S E-Hybrid

MSRP: $93,200

Miles per gallon equivalent: 50 combined

A 330-horsepower engine gets a 95-horsepower boost from an electric motor to move the Panamera from 0 to 60 in 5.2 seconds before topping out at 167 mph.

Formula One cars use that hybrid power in much the same fashion, though Porsche makes this hybrid look like a track-ready Prius. Still, a 7-inch touchscreen entertainment and communications system, an 11-speaker base sound system ( which bumps up to 16 speakers and 1,000 watts if you pick the Burmester High-End system), navigation, voice control, HD Radio, Bluetooth, apps, rear-seat multimedia players, a telephone module, automatic climate control and noise and heat insulation make it clear that this isn't the same hybrid your town is using in it municipal fleet to cut costs.

3. 2016 Mercedes-Benz S550e

MSRP: $95,650

Miles per gallon equivalent: 58 combined

Still one of the best bargains in the luxury category, which is tough to say with that price tag. For not one penny more than the 21.5-mpg base model, you can swap the 4-liter V8 engine and 449 horsepower in favor of the more-efficient, hybrid-aided 3-liter, 436-horsepower V6. That's not much of a loss

Meanwhile, you still get to play with 16-way power massaging ventilated leather seats, multicolor/multizone LED lighting, the fragrance system in the vents, the rear-seat refrigerator box, the 4-zone automatic climate control, the dual 12.3-inch entertainment and information screens, the COMAND information and entertainment system with touchpad controller, a Burmester surround sound system, free navigation, global radio, dual USB ports, 10-gigabyte music hard drive, in-car wi-fi and rear seat entertainment system. Unless you're looking to join a street-racing circuit in one of the nation's wealthier zip codes, you'll never miss the slightly more brawny gas version and you certainly won't miss the gas station.

2. 2016 Mercedes-Benz B250e

Starting price: $41,450

Miles per gallon equivalent: 83.5 combined

Electric charge range: 87 miles

Yes, it's kind of small and still looks like a luxury Nissan Leaf, but those 177 horsepower and has 43.6 cubic feet of cargo space with the seats down are no joke. Combine that with power front seats, dual-zone automatic climate control, HD radio, Bluetooth streaming and a mobile app to keep track of its diagnostic information remotely, and you have one formidable entry into the luxury electric sedan category. Right now, the B-Class electric drive is only available in 11 states (California, Connecticut, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Oregon, Rhode Island and Vermont), but it's a low-end option for those seeking efficient Mercedes-Benz luxury -- even if that luxury is still largely tucked away in options packages.

1. 2016 Tesla Model S

Starting price: $77,500 with incentives

Miles per gallon equivalent: 100 combined

Electric charge range: 270 miles

Still the king of the electric fleet, though the competition is creeping up. The 376-horsepower motor, 5.2-second 0-60 and 155 mph top speed all add up to more performance than any other electric vehicle can manage. Meanwhile, while not as efficient as the BMW i3's 124 mpge, that 270-mile range, supercharger and eight-year, unlimited mile warranty are unmatched. With charger-oriented navigation in place and self-driving “autopilot” making its way online, the Model S still makes a strong case for itself even as the cheaper Model 3 and more spacious Model X sport utility hit the market.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.