List price and insurance are the two biggest factors motorists consider when buying a new car, but running costs shouldn't be neglected either.
In fact, just how far you can go between trips to the pumps is important for many buyers as choosing an efficient car to suit your needs will save you a decent amount of money in the long run.
Economical cars are less harmful to the environment too and buying a new model with a CO2 score under 100g/km means you'll pay no road tax, so there's decent savings to be had by choosing wisely.
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Hybrid and electric cars may offer the cheapest running costs and the highest MPG scores, but they can be expensive to buy in the first place. Added to that many of them, particularly fully electric cars, may not fit into your lifestyle if you're driving plenty of miles.
Fortunately, many mainstream manufacturers now offer petrol and diesel-powered cars with MPG and CO2 figures good enough to rival many hybrids.
Official MPG figures are recorded using a flawed system and the figures manufacturers quote are difficult to obtain in real world driving. However, the tests are standardised so the cars they name as best-performing are the most frugal you can buy.
Here are some of the cheapest new cars to run that you can get your hands on.
Renault Clio 1.5 DCi
Another small French hatchback and a direct rival to the 208, the Renault Clio comes with an ultra-efficient, fuel-sipping mid-range engine.
The Clio 1.5 DCi ECO uses a 90bhp diesel four-cylinder capable of a combined 88.3mpg and CO2 emissions as low as 82g/km, making it road tax free, along with many of the cars on this list.
This version will set you back £15,225 new, but you'll need the additional £250 ECO pack to achieve these figures. The extra also includes longer gear ratios and thinner, low-rolling resistance tyres.
The Clio a chic supermini and hides its five doors well – the two rear door handles are tucked away neatly within the quarter window. Added to that, it's also comfortable and easy to drive, with a stylish cabin. However, some of its key rivals are slightly more spacious on the inside and while there's no obvious shortfalls, the likes of the Ford Fiesta are more fun to drive.
Vauxhall Corsa 1.3 CTDi ecoFlex
The most economical version of the Vauxhall Corsa – of which 92,077 were registered in the UK in 2015 – is the 1.3 CTDi ecoFlex model.
Is this spec, the 95bhp diesel-powered 1.3 Corsa will return 88.3mpg and CO2 emissions of 85g/km.
One of the real party pieces of the current generation Corsa is its price. The new model starts at just £8,995, undercutting some key rivals by four figures. However, the most economical choice comes at a premium. The 1.3 ecoFlex Corsa starts from £14,990 - a lot of money to fork out on a car starting from under nine grand.
Kia Rio 1.1 CRDi
The cheapest version of the 1.1 litre Kia Rio is priced from £12,245, but generates fuel consumption figures that "almost defy credibility", says the RAC.
The 74bhp three-cylinder diesel engine will see you get 88.3mpg and emit only 85g/km of CO2. And despite being a supermini, dimensions inside and boot space are impressive. It also has a five-star Euro NCAP safety rating and comes with the manufacturer's 100,000-mile seven-year warranty.
It's a sensible choice on paper but despite a fairly cheap price and low running costs, the entry level version of the Rio 1.1 CRDi has been criticised for not quite matching up to its rivals in terms of equipment. Maybe the best choice for those on a tight budget.
Ford Fiesta ECOnetic
Auto Express proclaims the Fiesta ECOnetic to be a great choice for motorists who want good economy without compromising on driving fun. The 1.5-litre TDCi ECOnetic version posts 85.6mpg and 87g/km CO2.
The Fiesta often comes out top of polls regarding the best driving C-Segment hatchbacks and Auto Express says the ECOnetic "retains the brilliant driving dynamics that have helped make the Fiesta a consistent top seller over the years".
The entry level ECOnetic fiesta is the 1.5 "Style" with 95bhp and stop/start technology as standard. It starts from £15,195.
Citroen C4 1.6 BlueHDi
Unlike the Fiesta, the Citroen C4 can't match its rivals when it comes to driving feel, although CarBuyer says it still offers low running costs, great practicality and comfort, making it an ideal economical car for motorway slogs.
In particular, the 1.6-litre BlueHDi car in Feel trim is an efficient and comfortable machine. Citroen claims just under 86mpg for the most frugal version of its family hatchback and while the soft suspension means the C4 isn't sharp, it's certainly a cosy place to be.
The interior is well made and comfortable and there's plenty of space up front for the driver and a passenger. However, space in the back isn't huge and the C4 serves up a 408-litre boot.
CO2 emissions come in at 86g/km, so this C4 is road tax free. Prices for the BlueHDI Feel start from £17,980, but the same engine can be bought on lower trim levels – on entry level Touch cars, it delivers 79mpg and starts from around £1,000 less.
Honda Civic 1.6i-DTEC
While MPG figures are sourced through official government testing procedures, many buyers prefer to base their purchases on real-world testing - and the Honda Civic 1.6i-DTEC comes out on top, according to What Car?.
Honda claims its Civic 1.6i-DTEC delivers up to 78.5mpg on a combined drive. However, tests on UK roads show it musters 67.2mpg.
The Civic is a spacious, good-to-drive family hatchback, although not quite on par with class leaders such as the Volkswagen Golf in terms of overall quality. Prices start at £19,400 and with CO2 emissions of 94g/km, you don't have to worry about tax.
Hyundai i20 CRDi Blue S
Official tests peg the Hyundai i20 CRDi Blue S as one of the most economical cars on sale, with figures as high as 88.3mpg in official testing. As such, Auto Express lists it as one of the cars you should consider for small fuel bills.
It uses a 1.1-litre diesel engine with 74bhp and emits 84g/km CO2, so again, it's free of road tax.
Auto Express is quick to point out that this is one slow car, though. It does 0-62mph in 16secs, which could be frustrating. However, it's an easy car to drive, especially around town, and the tall profile means there's generous amounts of space and equipment is generous. The Blue S comes in at £12,690.
Citroen C3 1.4 e-HDi 70 Airdream
It might not be one of the best small cars on sale, but according to What Car?, the Citroen C3 is one of the most efficient, achieving a real-world MPG score of 70.3mpg.
That could make it a tempting buy for those looking to guarantee lower fuel bills, although the overall picture is less enticing. In its full review, What Car? says the C3 is a stylish supermini that is big on comfort but poor to drive, while passenger space in the back is compromised.
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