Pickup trucks are not the first vehicles most people think of when the topic comes to fuel efficiency. Although these indispensable workhorses of the U.S. economy play a vital role in housing, repair & maintenance, and of course, recreation, they're not exactly the most economical.

In recent years, however, there have been some major improvements in pickup fuel economy. The biggest gains have been seen in full-size models, with the 2013 Ram 1500 V-6 and Ford F-150 V-6 being two noteworthy examples. Let's not forget that GM still produces the Chevrolet Silverado and GMC Sierra Hybrid (although it seems most customers have.) In commemoration of Earth Day 2013, we've rounded up the top 10 most fuel-efficient pickup trucks on sale today, and a sneak peak at a few fuel-sipping models to come.

1. 2013 Toyota Tacoma I-4 2WD Manual - 21 city/25 highway, 23 MPG Combined

Unsurprisingly, the pickup MPG champ is a midsize model: the four-cylinder Toyota Tacoma 2WD with the five-speed manual transmission. This model is the definition of a workhorse, with adequate power, and a no-frills interior. With just 159 hp and 180 lb-ft of torque on tap, there's two ways you can drive: Like you hate it, or chilled out. We'd recommend the latter for maximum efficiency; the first way makes more noise than momentum.

2. 2013 Nissan Frontier I-4 2WD Manual - 19 city/23 highway, 21 MPG Combined

Nissan's four-cylinder Frontier trails the Tacoma slightly in both economy and power, with its 2.5-liter I-4 serving up a mere 152 hp and 171 lb-ft of torque. Its 21 mpg combined economy is decent for a pickup, but considering that are now full-size models that return about the same economy with more power, we'd look further down the list for a more compelling combination of power and mileage.

3. 2013 Ram 1500 HFE - 18 city/25 highway, 21 MPG Combined

Here's where things start to get interesting. How would you like the economy of a midsize with the power and capability of a full-size? Ram has delivered that combination with the 2013 Ram 1500 HFE, which comes with grille shutters and auto stop-start. Its combined fuel economy matches the Nissan Frontier I-4 automatic with double the horsepower, 305 versus 152. Other than the Ram's bigger footprint, there isn't much downside to this model.

4. 2013 Toyota Tacoma I-4 2WD Automatic - 19 city/24 highway, 21 MPG Combined

The Tacoma four-cylinder automatic's story is similar to the Frontier's: Decent economy in exchange for less-than-thrilling performance. The Tacoma might have scored a little better if it wasn't saddled with an aged four-speed automatic. It may be a proven combination, but the downsides are obvious.

5. 2013 Chevrolet Silverado/GMC Sierra Hybrid - 20 city/23 highway, 21 MPG Combined

The Chevrolet Silverado and GMC Sierra hybrid are the only other full-size trucks that come close to matching the Ram HFE's fuel economy. An added bonus is V-8 power! It doesn't seem like there's much downside to this package until you realize the steep $42,000 price of entry plus considerably lower towing and payload ratings than their conventionally-powered cousins. Currently, GM is offering $4000 cash back on these to help clear them out ahead of the introduction of the all-new 2014 trucks, which won't be offered with a hybrid powertrain.

6. 2013 Ram 1500 V-6 - 17 city/25 highway, 20 MPG Combined

The 2013 Ram 1500 V-6 makes a second appearance on our list in non-HFE form. The "regular" V-6 skips the grille shutters and auto stop/start, sacrificing a mere one mpg in the city. After having spent more than a week in this model, we can say confidently that it delivers on its promise of economy and power.

7. 2013 Ford F-150 V-6 2WD - 17 city/23 highway, 19 MPG Combined

The Ford F-150 EcoBoost maybe the headline-grabber, but its less-glamorous naturally aspirated stablemate is is nothing to sneeze at. With 302 hp and 278 lb-ft of torque coming from its 3.7-liter V-6, this F-150 2WD delivers ample power and a respectable 19 mpg combined rating. Until the 2013 Ram came along, it was the full-size class leader. With the 2015 Ford F-150 just around the corner, don't expect Ram to hold that title without a fight.

8. 2013 Nissan Frontier I-4 2WD Automatic - 17 city/23 highway, 19 MPG Combined

We love the Frontier for its nimbleness and fun-to-drive character...just with the optional (and highly-recommended) 4.0-liter V-6. A gain of 109 hp and 110 lb-ft of torque over the base I-4 is well worth the sacrifice of 1 mpg in both city and highway fuel economy. Having driven both the four-cylinder and V-6 Frontiers, to say the difference is night and day is an understatement. This is again another model that doesn't make much sense unless you're getting an unbelievably smokin' deal on a lot-sitter the dealer's trying to clear out.

9. 2013 Nissan Frontier V-6 2WD - 16 city/22 highway, 18/19 MPG Combined (automatic/manual)

This is one configuration of the Frontier we can confidently recommend, especially with the 2013 model's incremental fuel economy gain of 1 mpg in the city and 2 mpg on the highway. The EPA gives a slim 1 mpg combined edge to the manual, although both the slushbox and row-yourself versions have the same rating of 16 city and 22 highway. With a robust 261 hp and 281 lb-ft of torque, the V-6 Frontier acquits itself nicely in all situations, and handles midsize loads with ease.

10. 2013 Ford F-150 EcoBoost 2WD - 16 city/22 highway, 18 MPG Combined

Ford's high-tech performance poster boy makes it on our list, albeit barely. Despite just squeaking onto our fuel-sipper list, it took the top power prize with its 365 hp and 420 lb-ft of torque. The twin-trubo EcoBoost V-6 definitely delivers on the power front, and if you can refrain from indulging in the "boost" part too often, acceptable fuel economy. Still, the model has gotten a reputation among some truck enthusiast circles of falling short of its economy promise.


Future Contenders:

2014 Ram 1500 EcoDiesel

Not content to have the full-size fuel economy crown just for the 2013 model year, Ram looks like it wants to be number one with a bullet with the 2014 Ram 1500 EcoDiesel, which will share its 3.0-liter turbodiesel V-6 with the 2014 Jeep Grand Cherokee EcoDiesel when it goes on sale later this year. Final figures for this engine in the Ram have not yet been announced, but if the Jeep is anything to go by, we can expect at least 240 hp, 420 lb-ft of torque, and highway fuel economy in the high 20s -- some believe possibly even 30 mpg in 2WD trim. Although likely to carry a significant price premium, probably at least $4000 if not more, the first diesel half-ton truck could considerably shake up the full-size truck market..

2014 Chevrolet Colorado

Another shakeup in the truck market could be coming in calendar-year 2014 if the rumored diesel version of the next-generation Chevrolet and GMC midsize truck becomes reality. News has recently broken that GM may drop the Colorado/Canyon names, but more significant than the name change is what might be under the hood. We're expecting GM's direct-injected 2.5-liter I-4 and 3.6-liter V-6 will be among the offerings, and should offer very good fuel economy for the class.

The potential MPG chart-topper could be the 2.8-liter I-4 Duramax diesel offered in the global Colorado, which produces 177 hp and 347 lb-ft in overseas trim. Those figures may drop slightly to bring it into compliance with U.S. emissions laws, but regardless, if it is offered in the U.S., it promises to deliver an outstanding balance of torque and fuel efficiency. The option price is unknown, but may run between $2500 and $3000. Whether diesel will pay off for GM in the price-sensitive midsize market remains to be seen, but if GM's midsize diesel is a hit, expect other manufacturers to follow suit.