Most fuel-efficient cars

We spend an awful lot on fuel over a driving lifetime, so make sure your car insurance is the right price for your budget.

It's fair to say that we're extraordinarily keen to help drivers save money on car insurance by comparing policies - but there are other ways you can keep your motoring costs down too.

After you've paid for the standing costs, or essentials, of car ownership - car loan, insurance, car tax and MOTs - you have your running costs.

They're the day-to-day costs of using your car - and of these, fuel is probably the biggest expenditure you'll have.

So how can you keep your fuel costs down?

What is good fuel economy?

We asked Stuart Masson, the driving force behind popular blog The Car Expert, about the benchmarks around mpg figures.

"There's definitely an element of horses for courses about fuel economy," he says, "as the most economical type of vehicle will largely depend on your driving requirements.

"If a car is working hard to deliver performance, then it will use more fuel than one that's doing the job more easily - even if the official figures say otherwise," he explains.

"Good fuel economy is a complex science and the industry measurements are - at best - only guides to what you can expect for your own specific circumstances."

It sounds a bit complicated, but all this really means is that you have to think about how you're going to use your car before working out which models will be more fuel efficient for your needs.

There's no such thing as a standard 'good' mpg, because it varies according to the type of car and what you need from it.

Top tip: You need to work out which type of car suits your needs best, then look for the cars in that bracket with best fuel efficiency.

Diesel or petrol: which is more economical?

Stuart emphasises that this very much depends on your driving needs. "If you're doing longer-distance runs, particularly on motorways, or carrying heavy loads, then a diesel is usually much more efficient.

"If you do a lot of short stop-start trips (like city driving), then a petrol car can usually hold its own against a similar diesel, potentially delivering better performance."

Read more about how to find cheap fuel.

What about hybrids?

Just because it's a hybrid or eco vehicle doesn't necessarily mean it has better fuel efficiency, cautions Stuart.

"Again, it depends how the car is used and whether that use suits a hybrid system.

"On motorway trips, the batteries are used up in a matter of minutes and from then on you're just dragging a couple of hundred kilos of dead battery with you - which is not good for fuel economy."

Do low emissions mean better fuel economy?

In theory, yes.

"A car with a lower emission rating is usually using less fuel as well - in fact, there's a roughly linear relationship under most circumstances - so it should be cheaper to run," advises Stuart. 

However, it does get more complicated than that and, again, it also depends on how the car is being driven.

"The VW emissions scandal has raised many legitimate questions about how we look at economy and emissions - all we have to go on are the official lab measurements."

Official mpg versus true mpg

Once you start taking an interest in car reviews, it doesn't take long before you register that the official mpg for cars is rarely the same as that experienced by the reviewer.

Admittedly, the two figures are closer in some than in others - it can vary from 5% to more than 40%.

Stuart explains why this is the case: "The official EU lab tests are insufficient for accurately testing modern cars.

"Not enough load is being put on the car, so it doesn't have to work very hard.

"In the real world, we drive our cars much harder than they do in the lab tests, even if we're not trying to.

"If you drove your car the way the lab testers 'drive' theirs, you'd never get to where you're going!

"Also, the car manufacturers have all become very good at 'optimising' their cars for performance in lab test situations, even if that means that real-world performance is compromised."

Top tip: Take more notice of the fuel efficiency figures achieved by reliable reviewers than manufacturers.

That said, the manufacturer's figures are useful for comparing similar car models, as every new car has been tested in the same controlled conditions.

And there is encouraging news around this issue - next year there will be a new economy test cycle that will provide a better 'real world' guide to the kind of economy you can expect, and manufacturers will be quoting these figures from 2019 onwards.

But for now, take mpg stats with a pinch of salt.

What is a good mpg?

As you've probably guessed by now, this depends on your circumstances - and the same car can deliver very different economy results in different conditions, or with added passengers and luggage.

However, we've pulled out some good examples you could use as a benchmark, below.

Does fuel efficiency affect your insurance?

Fuel efficiency alone isn't a factor in determining which insurance group your car falls in - which in turn dictates the cost of your insurance - but cars with smaller, low-powered engines do tend to be cheaper to insure, and they also often have good fuel efficiency.

So indirectly, choosing a car with good fuel efficiency may keep your insurance costs down.

There are lots of factors determining your insurance, though, so if you add lots of expensive trims to your fuel-efficient car, that will bump up your premiums. 

The most economical small city car

In Whatcar?'s summer 2017 reviews, the Suzuki Celerio 1.0 came out best in this category, with an official mpg of 65.7 and a 'true' value of 57.8 mpg.

The most fuel-efficient family car

Again, looking at Whatcar?'s summer tests, the Vauxhall Astra 1.6CDTi 110 Ecoflex came out best in this group, with its official mpg coming in at 83.1 and tested value at 56.3 mpg.

The most efficient luxury car

The BMW 7 Series 730d saloon comes out well here, according to Carbuyer.co.uk, which tested it in summer 2017 and gave it an mpg of up to 60 mpg - very close to its official rating of 56.

By Katrina Hendley