What are the Most Fuel Efficient Cars?

In the search for your next car, it’s easy to become overwhelmed by all the flashy looks, tech-savvy interiors, special offers and abundance of model variants. It’s often the case that these things quickly take a seat in the face of what we really care about - saving money in the long run. Looking for the most fuel-efficient cars is a great place to start, and we are here to help. From SUVs to petrol and diesel models, these fuel-efficient machines might already have the exact looks and tech that you’ve been searching for. Find out more below.

Our Most Fuel-Efficient SUVs​

Suzuki Ignis. This deceptively spacious car gives many of its compact SUV competitors a run for their money with a superb 1.2L hybrid petrol engine. Suzuki has created a great city-country balance in the Ignis, feeling more than comfortable in both settings via its compact nature and four-wheel drive options. At lower engine speeds, the hybrid system kicks in to provide great consistency in engine power which performs great in slow city driving or slow backroad trekking. Even at higher speeds with the 4-wheel drive option, the Ignis achieves up to 59 mpg! A unique look sets it apart while a modern interior provides all your needs of entertainment, driver assistance and navigation.​

Mazda CX-5. Taking a big leap in SUV size, we find the high-quality yet affordable Mazda CX-5. The 2.2-litre diesel engine seems perfectly synchronised to its automatic gearbox and offers up to 50mpg and even for a 2.0-litre petrol variant, you can find a fuel consumption of up to 44mpg. Beyond this, there’s a range of trim levels available, each offering a generous array of tech to suit your needs. Of course, Mazda hit the nail on the head with its quick handling and low vibration/low noise ride. We can talk about the CX-5 for ages, but from what we’ve said so far, it’s easy to see why it has continued to gather awards and popularity to this day.  

Peugeot 2008. A newfound favouritism has been widely given to Peugeot’s latest models due to their style and ease of use, and the 2008 is taking the reins. But it doesn’t stop at head-turning looks; the Peugeot 2008 ticks all the boxes for fuel efficiency too. Its 1.2-litre PureTech petrol engine can return just over 53 mpg which makes the 2008 not just a pretty face. Pair this with an impressive array of features that come standard even on the entry-level trim, and you’ll see why so many place the 2008 at the top of their wish lists. An electric version is out too, the e-2008, which is in a sense the most “fuel-efficient” you can get, so be sure to check that out too.

The Most Fuel-Efficient Petrol Cars

Mazda 2. Shuffling away from the SUV market, the Mazda 2 is a great hatchback option for those who wish for a good deal of style alongside a fuel-efficient system. You’re given the choice of two petrol engines, one with and one without mild hybrid technology, although the former will provide a little extra kick with 89bhp. Additionally, this mild hybrid system keeps running costs at a minimum with an impressive economy of up to 60mpg and a low emissions bracket. A nicely weighted steering gives substance to the 2’s sporty appearance, while a firm ride develops a good level of control over uneven surfaces without becoming uncomfortable. Despite its size, the Mazda 2’s tall interior design allows for plenty of headroom, even in the rear.​

Suzuki Swift. As you may know, the Swift and indeed much of the Suzuki fleet holds a competitive edge against other mainstream rivals due to its ability to pack a lot of specs in while maintaining a surprising degree of affordability. The Swift is sparing with fuel, with even the most demanding combination still returning over 52 mpg, while at best the manual transmission offers over 59mpg. What sets the Swift apart is its variety of trim levels and its sportier model, the Swift Sport. The Swift is more than fun to drive and comes with a mild hybrid system as standard which gives reason to its impressive economy. A decent front and rear space can handle adult passengers with room left over, making the Swift unexpectedly practical for its size.​

Mazda 3. Going back over to the Mazda fleet, the 3 might appeal to those who are seeking a bigger hatchback with a different styling attitude. Inside, the Mazda 3 gives a high-end luxury design which goes against the grain of its affordable pricing – just one of the many reasons why competitors find it so hard to triumph over the Mazda 3. As for the engine, the 2-litre petrol ‘e-Skyactiv X’ variant achieves over 54mpg which is impressive for its size and power, while other variants like the less powerful Skyactiv-G can still achieve over 43mpg. After scanning the long list of equipment, options and extras that come on the entry-level Mazda 3, its affordability seems like a generous statement. From comprehensive infotainment systems, cruise control, parking aids and more, the Mazda 3 is most certainly a slick fuel saver that should be on your radar.​

The Most Fuel-Efficient Diesel Cars

Peugeot 208. With recent 208 models showing a lighter structure and more aerodynamic profile, it’s expected that their fuel efficiency will be increased no matter what. The 1.5-litre diesel engine can achieve a real-world economy of well over 60mpg and emerges as a reliable choice against its competitors as a tried and tested powertrain. The modern 208s are completely different to their predecessors, bringing them into a new light of popularity. Offering a comfortability that rivals larger cars, an eye-catching style, and a lean handling profile, it’s clear why the Peugeot 208 was Europe’s best-selling car last year.

Vauxhall Astra. There are a few engine variants on the Astra, from Petrol to Diesel and from Hybrid to Electric, but the 1.5-litre diesel deserves a mention here. Its muscularity at lower revs matches the Astra's already muscular profile which makes it seem like they were built for each other. The diesel engine effortlessly works wonders even with a full passenger load with its 130hp and can easily achieve well over 60mpg in the real world. The most popular GS trim level features sportier styling, keyless entry, heated seating and much more, although the entry-level Design trim comes with plenty of equipment as standard for you to explore.

Peugeot 308 SW. With a plush ‘i-Cockpit’ inside and refined exterior, the 308 SW is an estate that perfectly balances efficiency and cost with its frugal diesel engine and 600L+ boot space. The 1.5L diesel engine offers impressive power which can be adapted with three driving modes: Eco, Normal and Sport. A fuel economy of over 54mpg is more than enough to handle its use as an estate, while a range of trims can provide for your individual needs. The ‘Drive Assist Pack’ comes as standard offering a range of tools to help you focus on even the longest of commutes such as blind spot detection, cruise control, cross-traffic alert, and more.

What Makes a Car Fuel Efficient?

The fuel efficiency of a car is determined by the fuel it uses and the engine that burns it. The energy density of a fuel is a measure of how much energy you get out of burning it. Because diesel is much more energy-dense than petrol, it is typically more efficient – you get more bang for your buck. Additionally, petrol needs to be combusted in a spark-ignition engine while diesel can be combusted in a compression engine. Compression engines have a higher thermal efficiency than spark ignition engines (they convert more heat into mechanical energy).

Compression engines, which ignite diesel and air to move the pistons, can operate at hotter temperatures than spark-ignition engines. This means that for spark-ignition engines, more petrol needs to be mixed with the air before it’s burned so the engine doesn’t overheat (i.e., injecting less petrol will make it too hot, while compression engines have better thermal efficiency and don’t always need to mix additional diesel to cool it down). This is the key difference in engine efficiency. Additional petrol is always mixed, thereby intentionally wasted, just to ensure the engine is working at its optimal thermal efficiency. Diesel engines operate more frequently at an optimal diesel-air ratio, therefore making them more efficient.

This also means that a fuel-efficient petrol car is partly determined by how much intentionally wasted fuel is injected into the ratio just to keep the engine cool. The higher the thermal efficiency of the petrol engine, the less fuel that needs to be additionally mixed.