Introduction
Fuel efficiency and low running costs aren't always the same thing. A car can be genuinely cheap to insure and tax without necessarily being the most efficient at the pump. The most fuel efficient cars on the market span everything from small self-charging hybrids to genuinely luxurious plug-in saloons.
Quick picks:
- Highest official MPG figure: BMW 330e and Mercedes-Benz E300 de, both officially rated up to 217.3mpg as plug-in hybrids, provided the battery stays charged.
- Best small hybrid efficiency: Mazda2 Hybrid, officially rated between 67.3 and 74.3mpg.
- Best non-hybrid choice: Vauxhall Corsa 1.5 Turbo D, returning up to 70.6mpg from a conventional diesel engine.
- Best all-round self-charging hybrid: Toyota Prius, officially rated at 67.0mpg with no plugging in required.
What Are the Most Fuel Efficient Cars?
The best fuel-efficient cars to buy in the UK depend entirely on your daily driving routine, as city hybrids excel in stop-start traffic while modern diesels remain the unmatched king of long-distance motorway efficiency.
Here are 10 real examples with verified MPG figures and engine sizes for each.
| Car | Engine | Official MPG |
|---|---|---|
| Toyota Prius | 1.8 litre full hybrid | 67.0 |
| Toyota Corolla Hybrid | 1.8 litre full hybrid | 63.8 |
| Hyundai Ioniq Hybrid | 1.6 litre full hybrid | 62.8 |
| Kia Niro Hybrid | 1.6 litre full hybrid | 64.2 |
| Mazda2 Hybrid | 1.5 litre full hybrid | 67.3 to 74.3 |
| BMW 330e | 2.0 litre petrol plug-in hybrid | Up to 217.3 |
| Mercedes-Benz E300 de | 2.0 litre diesel plug-in hybrid | Up to 217.3 |
| Peugeot 208 | 1.5 litre diesel | 71.4 |
| Vauxhall Corsa 1.5 Turbo D | 1.5 litre turbo diesel | 70.6 |
| Renault Clio E-Tech | 1.6 litre full hybrid | Around 64 to 67 |
MPG figures throughout this guide are based on official WLTP combined fuel economy data published by manufacturers. Real-world fuel economy may vary depending on driving style, vehicle condition, weather and journey type. Treat these figures as a genuine benchmark for comparison rather than a guarantee of what you'll personally achieve.
1. Toyota Prius - 67.0mpg
The Toyota Prius uses a 1.8 litre self-charging hybrid system, officially rated at 67.0mpg, remaining the benchmark most rivals get measured against. Decades of continuous development have kept Toyota's hybrid technology consistently ahead of most competitors, with no need to ever plug the car in to achieve the headline figure.
Best For
- Drivers wanting hybrid efficiency without home charging
- Mixed urban and motorway driving
- Long-term reliability alongside strong economy
2. Toyota Corolla Hybrid - 63.8mpg
Sharing much of its 1.8 litre hybrid system with the Prius, the Corolla Hybrid officially returns 63.8mpg in a more conventional hatchback and estate body style, suiting buyers wanting Prius-level efficiency without the more distinctive styling, at a very similar running cost.
Best For
- Buyers wanting hybrid efficiency in a more traditional body style
- Family hatchback or estate practicality
- Long motorway commutes
3. Hyundai Ioniq Hybrid - 62.8mpg
The original Ioniq uses a 1.6 litre hybrid system, officially rated at 62.8mpg, remaining one of the most aerodynamically efficient cars ever produced. Now settled into the affordable used bracket, it represents genuine value for buyers specifically prioritising efficiency over badge prestige.
Best For
- Buyers prioritising efficiency above brand recognition
- Value focused used hybrid buyers
- Aerodynamic, motorway-friendly driving
4. Kia Niro Hybrid - 64.2mpg
The Niro combines SUV-shaped practicality with a 1.6 litre full hybrid system officially rated at 64.2mpg. It's one of the more spacious options on this list, making it a sensible choice for buyers who want efficiency without sacrificing everyday practicality.
Best For
- Buyers wanting SUV practicality with hybrid running costs
- Families needing genuine boot and passenger space
- Mixed driving rather than purely urban use
5. Mazda2 Hybrid - 67.3
Built on shared hybrid technology, the Mazda2's 1.5 litre hybrid system officially returns between 67.3 and 74.3mpg, one of the strongest figures on this list from a genuinely compact car, performing particularly well in stop-start urban driving where hybrid systems do their best work.
Best For
- City commuters wanting the lowest possible fuel spend
- Buyers wanting a less common hybrid badge
- Short, urban-heavy journeys
6. BMW 330e - 217.3mpg
The BMW 330e pairs a 2.0 litre petrol engine with an electric motor, officially rated up to 217.3mpg provided the battery stays charged, alongside an electric-only range of around 30 miles, proving fuel efficiency and genuine performance aren't mutually exclusive by reaching 0 to 62mph in under six seconds while still capable of covering short journeys on electric power alone.
Best For
- Buyers wanting genuine performance alongside efficiency
- Short commutes with reliable home charging
- A more premium interior and badge
7. Mercedes-Benz E300 de - 217.3mpg
Pairing a 2.0 litre diesel engine with an electric motor, the Mercedes-Benz E300 de is officially rated up to 217.3mpg, matching the BMW 330e, with a similar electric-only range of around 30 miles. The diesel pairing gives it a genuine advantage over petrol-based plug-in hybrids on longer journeys once the battery is depleted.
Best For
- Longer distance drivers wanting plug-in efficiency
- Buyers wanting genuine luxury alongside low running costs
- Company car drivers benefiting from lower tax rates
8. Peugeot 208 - 71.4mpg
The Peugeot 208 diesel uses a 1.5 litre engine officially rated at 71.4mpg, one of the strongest non-hybrid figures on this list, combining genuine efficiency with distinctive styling and an unusually driver-focused dashboard layout compared to most rivals in the class.
Best For
- Buyers wanting strong diesel economy without hybrid technology
- Longer motorway journeys
- Distinctive styling in a supermini package
9. Vauxhall Corsa 1.5 Turbo D - 70.6mpg
Sharing its 1.5 litre turbo diesel engine with the Peugeot 208, given both brands sit under the same parent group, the Vauxhall Corsa officially returns up to 70.6mpg. It's proof that genuinely strong efficiency doesn't require hybrid technology at all, provided the engine underneath is well engineered.
Best For
- Buyers wanting strong efficiency without hybrid complexity
- Straightforward, simple mechanical ownership
- Longer journeys favouring diesel economy
10. Renault Clio E-Tech - 67mpg
A full hybrid using a 1.6 litre engine, the Renault Clio E-Tech typically returns around 64 to 67mpg in official testing, competitive with the strongest small hybrids on this list, and also holds its value reasonably well on the used market, helping offset the higher purchase price hybrid technology typically commands.
Best For
- Buyers wanting hybrid efficiency with strong resale value
- City and mixed driving
- A tight budget wanting maximum value from a used hybrid
Why Does Fuel Efficiency Vary So Much Between These Cars?
Not all efficient cars work the same way. The engine and drivetrain matter more than the badge on the back. A full hybrid, like the Prius, Corolla, Ioniq, Niro, Mazda2 and Clio E-Tech here, charges its own battery automatically through driving and braking, running on electric power alone at low speeds where most of the efficiency gain comes from.
A plug-in hybrid, like the BMW 330e and Mercedes E300 de, works differently, carrying a much larger battery charged from the mains. The extraordinary official figures these two achieve, over 200mpg, only apply when the battery is charged daily and most journeys stay within the roughly 30 mile electric-only range.
Left uncharged, a plug-in hybrid becomes a heavier, less efficient version of a standard car, covered in full in our guide on petrol versus diesel versus hybrid.
The Peugeot and Vauxhall entries prove a third route entirely. Neither uses any hybrid assistance at all, relying purely on efficient, modern diesel engineering to reach figures that rival many hybrids, particularly useful for buyers covering higher motorway mileage where diesel's traditional efficiency advantage still holds up well.
What Would Each Car Actually Cost You in Fuel?
Official MPG figures only become meaningful once you translate them into real pounds and pence. Based on current UK average fuel prices of around 158.74p per litre for petrol and 184.11p per litre for diesel, here's what 10,000 miles would cost in fuel for each car on this list.
| Car | MPG | Fuel cost for 10,000 miles |
|---|---|---|
| BMW 330e | Up to 217.3 | Around £330, only if charged regularly |
| Mercedes-Benz E300 de | Up to 217.3 | Around £385, only if charged regularly |
| Mazda2 Hybrid | 67.3 to 74.3 | Around £1,020 |
| Toyota Prius | 67.0 | Around £1,080 |
| Renault Clio E-Tech | Around 64 to 67 | Around £1,100 |
| Toyota Corolla Hybrid | 63.8 | Around £1,130 |
| Kia Niro Hybrid | 64.2 | Around £1,125 |
| Hyundai Ioniq Hybrid | 62.8 | Around £1,150 |
| Peugeot 208 | 71.4 | Around £1,170 |
| Vauxhall Corsa 1.5 Turbo D | 70.6 | Around £1,185 |
The gap between the BMW and Mercedes plug-in hybrids and everything else on this list looks dramatic, holding up only if the battery genuinely gets charged daily and most journeys stay within electric range. Left uncharged, both would cost considerably closer to, or even more than, the full hybrids and diesels on this list since a heavier, unused battery pack works against efficiency rather than for it.
Frequently Asked Questions
Which car in the UK is the most fuel-efficient?
Among genuinely everyday, easy-to-own cars, the Toyota Prius leads this list at 67.0mpg without ever needing to plug in. The BMW 330e and Mercedes-Benz E300 de officially rate higher still, up to 217.3mpg, but only achieve this consistently if charged daily.
What car gets 70 MPG?
Three cars on this list cross that mark. The Mazda2 Hybrid reaches up to 74.3mpg, the Peugeot 208 diesel returns 71.4mpg, and the Vauxhall Corsa 1.5 Turbo D returns 70.6mpg, each achieving this without relying on plug-in charging.
Which car is the cheapest to run in the UK?
Fuel efficiency is only one part of overall running cost, alongside insurance, tax and maintenance. For a full breakdown weighing all of these together rather than fuel economy alone, see our guide on the cheapest cars to run in the UK.
Why do plug-in hybrids show such extreme official MPG figures?
Because the official test assumes the battery starts fully charged and much of the test distance is covered on electric power alone. Real-world figures drop considerably once the battery depletes and the petrol or diesel engine takes over full time.
Is a diesel engine ever more efficient than a hybrid?
Yes, particularly on longer, motorway-heavy journeys. The Peugeot 208 and Vauxhall Corsa here both demonstrate that a well engineered modern diesel can match or beat many hybrids without any electric assistance at all.
Do BMW and Mercedes plug-in hybrids cost more to maintain than a Toyota hybrid?
Generally yes, reflecting both brands' premium positioning and the added complexity of a larger plug-in battery system, though servicing costs vary considerably by specific model and dealer network.
Which car on this list is cheapest to buy used?
Typically the Hyundai Ioniq Hybrid and Renault Clio E-Tech, both settled into a more affordable used bracket compared to the premium BMW and Mercedes plug-in hybrids on this list.
Does official MPG always match real-world driving?
Rarely exactly, though the gap tends to be smaller for full hybrids than for plug-in hybrids specifically since a plug-in's official figure depends so heavily on charging habits that real-world results vary enormously between owners.
At Car Planet, hybrid models like the Toyota Prius, Corolla Hybrid and Kia Niro consistently rank among the most popular choices for buyers looking to reduce fuel costs without switching to a fully electric vehicle.
Browse our full range of used hybrid cars at Car Planet, with real fuel economy details clearly listed on every vehicle we sell.
